---
title: China's great rivers: the finless porpoise, the lost baiji, Chinese… — how Mova does on the tests · Biology
description: Lesson 379 of the biology course of Mova's primary school: 3 of 11 tests right, exam 3 of 4, every question with the options, the student's choice, the right answer and why it chose.
---

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# China's great rivers: the finless porpoise, the lost baiji, Chinese alligators and sturgeon

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**Tests:** 3 of 11 right · **Exam:** 3 of 4 right · **Kind:** ★★ · **Understood:** 9 of 15 · **Run:** 2026-10-18, commit `f3c23ea72`

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Lesson 379 of the biology course of Mova's primary school, as Mova's small model took its tests: it had read this lesson and the ones before it and learned from their exercises. Each test shows the options in the order the student saw them, its choice, the right answer, the score of every option and why it chose. The lesson itself, sentence by sentence with trees and pragmatics: [the lesson in the corpora](https://md.mova.elamur.ai/free/en/corpora/school/biology/379-china-s-great-rivers-the-finless-porpoise-the-lost-baiji-chinese-alligators-and-sturgeon/).

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Every question of this lesson and each of its options parsed by Mova, with trees and pragmatics: [the lesson's questions in the corpora](https://md.mova.elamur.ai/free/en/corpora/questions/biology/379-china-s-great-rivers-the-finless-porpoise-the-lost-baiji-chinese-alligators-and-sturgeon/).

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### Test 1 · ★★ · wrong ✗ {#t1}

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Count them: a survey boat sees 3 finless porpoises and 2 dolphins from the sea. How many back fins?

- **1.** 3 — **← Mova's choice** · no support
- **2.** 0 — no support
- **3.** 5 — no support
- **4.** 2 — **✓ the right answer** · no support

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**Why:** No option found support in what it remembers, so it guessed: it took the first option shown. · [the question and its options parsed, with trees and pragmatics](https://md.mova.elamur.ai/free/en/corpora/questions/biology/379-china-s-great-rivers-the-finless-porpoise-the-lost-baiji-chinese-alligators-and-sturgeon/t1/)

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### Test 2 · ★★ · right ✓ {#t2}

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Count them: there are 2 kinds of alligator. How many kinds live in China?

- **1.** 1 — **← Mova's choice** · **✓ the right answer** · score 6
- **2.** 2 — score 6
- **3.** 0 — score 6
- **4.** 3 — score 6

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**Why:** It took the question to ask what it is done to. It chose option 1 with score 6, tied with another option at 6 (the first shown, or the one claiming less beyond what it knows, wins). Its support: lesson 316, line 5: «There are over 2,000 kinds of rodent, about four in ten mammal kinds, living on every continent except Antarctica, from tiny mice to the capybara.», reached through the remembered sentence the question matched. What matched: the same action «live» (+5); the same doer «2,000 kinds» (+1). · [the question and its options parsed, with trees and pragmatics](https://md.mova.elamur.ai/free/en/corpora/questions/biology/379-china-s-great-rivers-the-finless-porpoise-the-lost-baiji-chinese-alligators-and-sturgeon/t2/)

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### Test 3 · ★★ · wrong ✗ {#t3}

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Count them: a fishing ban starts in 2021 and lasts 10 years. In which year does it end?

- **1.** 2030 — **← Mova's choice** · no support
- **2.** 2041 — no support
- **3.** 2011 — no support
- **4.** 2031 — **✓ the right answer** · no support

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**Why:** No option found support in what it remembers, so it guessed: it took the first option shown. · [the question and its options parsed, with trees and pragmatics](https://md.mova.elamur.ai/free/en/corpora/questions/biology/379-china-s-great-rivers-the-finless-porpoise-the-lost-baiji-chinese-alligators-and-sturgeon/t3/)

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### Test 4 · ★★ · wrong ✗ {#t4}

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In a cartoon a river dolphin looks for fish with big shining eyes. What is right about the baiji?

- **1.** It hunted only in clear water — score 4
- **2.** It had huge eyes that glowed in the dark muddy water — **← Mova's choice** · score 5
- **3.** It was almost blind and found fish by clicks and echoes — **✓ the right answer** · score 5
- **4.** It found fish by smell alone — score 5

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**Why:** It took the question to ask which statement is true. It chose option 2 with score 5, tied with another option at 5 (the first shown, or the one claiming less beyond what it knows, wins). Its support: lesson 232, line 14: «A cat's eyes seem to glow in the dark because a shiny layer at the back of the eye reflects light that comes in; no eye makes its own light.», reached through the option's own match among the sentences about the question's things. What matched: the same place «dark» (+4); the same action «glow» (+1). The right option, 3, scored 5. · [the question and its options parsed, with trees and pragmatics](https://md.mova.elamur.ai/free/en/corpora/questions/biology/379-china-s-great-rivers-the-finless-porpoise-the-lost-baiji-chinese-alligators-and-sturgeon/t4/)

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### Test 5 · ★★ · wrong ✗ {#t5}

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«the porpoise isn't even caught, so why would a fishing ban help it» What is right?

- **1.** Porpoises eat fishing nets — **← Mova's choice** · no support
- **2.** More fish in the river means more food, and fewer nets to tangle in — **✓ the right answer** · no support
- **3.** It would not help at all, because nets and fishing boats never hurt porpoises — no support
- **4.** The ban makes porpoises grow fins — no support

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**Why:** No option found support in what it remembers, so it guessed: it took the first option shown. · [the question and its options parsed, with trees and pragmatics](https://md.mova.elamur.ai/free/en/corpora/questions/biology/379-china-s-great-rivers-the-finless-porpoise-the-lost-baiji-chinese-alligators-and-sturgeon/t5/)

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### Test 6 · ★★ · wrong ✗ {#t6}

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How would you find your way if loud engine noise filled your ears and you used sound to see?

- **1.** You would just use your eyes instead, as baiji did in muddy water — no support
- **2.** Noise makes echoes louder — **← Mova's choice** · score 2
- **3.** You would get lost, like a baiji whose echoes were drowned out — **✓ the right answer** · no support
- **4.** You would see better — no support

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**Why:** It took the question to ask what something is like. It chose option 2 with score 2, the only option with support. Its support: lesson 374, line 13: «Dolphins rely on sound to hunt and to talk, so loud noise can hurt or confuse them.», reached through the option's own match among the sentences about the question's things. What matched: the same doer «loud noise» (+2); it fills the role the question asks for (+1). Against it: the same property (-1). The right option, 3, found no support in what it remembers. · [the question and its options parsed, with trees and pragmatics](https://md.mova.elamur.ai/free/en/corpora/questions/biology/379-china-s-great-rivers-the-finless-porpoise-the-lost-baiji-chinese-alligators-and-sturgeon/t6/)

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### Test 7 · ★★ · wrong ✗ {#t7}

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«dams are clean power so they're all good, end of» What is the careful answer?

- **1.** Dams help fish lay more eggs — no support
- **2.** Dams never harm anything, because the water still flows through them — no support
- **3.** Dams make clean power but can block fish from where they lay eggs — **✓ the right answer** · score -1
- **4.** Dams make rivers dirtier only — **← Mova's choice** · score 1

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**Why:** It took the question to ask which statement is true. It chose option 4 with score 1, against -1 for the next best. Its support: lesson 283, line 12: «Beaver dams slow floods, clean water and make ponds full of life, though some farmers worry about flooded fields.», reached through the option's own match among the sentences about the question's things. What matched: the same action «make» (+1). The right option, 3, scored -1. · [the question and its options parsed, with trees and pragmatics](https://md.mova.elamur.ai/free/en/corpora/questions/biology/379-china-s-great-rivers-the-finless-porpoise-the-lost-baiji-chinese-alligators-and-sturgeon/t7/)

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### Test 8 · ★★ · right ✓ {#t8}

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What could have been done 30 years earlier to save the baiji?

- **1.** Limit nets, electric fishing and boat noise and protect its river — **← Mova's choice** · **✓ the right answer** · no support
- **2.** Paint the river blue — no support
- **3.** Move all the last baiji far away to the salty Black Sea, where boats are fewer — no support
- **4.** Teach it to see in the dark — no support

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**Why:** No option found support in what it remembers, so it guessed: it took the first option shown. · [the question and its options parsed, with trees and pragmatics](https://md.mova.elamur.ai/free/en/corpora/questions/biology/379-china-s-great-rivers-the-finless-porpoise-the-lost-baiji-chinese-alligators-and-sturgeon/t8/)

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### Test 9 · ★★ · right ✓ {#t9}

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«chinese alligator, so it's huge like the american ones» What is right?

- **1.** It is as long and heavy as a bus — no support
- **2.** It is the biggest reptile in the world — no support
- **3.** It is small, about 1.5 metres — **← Mova's choice** · **✓ the right answer** · score 2
- **4.** It is a kind of lizard that flies — score 1

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**Why:** It took the question to ask which statement is true. It chose option 3 with score 2, against 1 for the next best. Its support: lesson 379, line 14: «The Chinese alligator is small, about 1.5 metres, spends the winter asleep in burrows, and only a few hundred live wild, but zoos have bred many and some were…», reached through the option's own match among the sentences about the question's things. What matched: the same property (+1); the same light verb (be, have, do, get, go) (+1). · [the question and its options parsed, with trees and pragmatics](https://md.mova.elamur.ai/free/en/corpora/questions/biology/379-china-s-great-rivers-the-finless-porpoise-the-lost-baiji-chinese-alligators-and-sturgeon/t9/)

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### Test 10 · ★★ · wrong ✗ {#t10}

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Why might a dam harm a fish that lives far downstream?

- **1.** Dams drink all the water — no support
- **2.** It blocks the fish from swimming up to where it lays eggs — **✓ the right answer** · score 2
- **3.** Fish are scared of the dam's dark shadow and will not swim anywhere near it — **← Mova's choice** · score 3
- **4.** Dams make the fish forget the way — score 2

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**Why:** It took the question to ask which statement is true. It chose option 3 with score 3, against 2 for the next best. Its support: lesson 203, line 13: «Fish notice movement and shadows, which often mean a bird is hunting, and they also feel movements in the water with a line of sensors along their sides called…», reached through the option's own match among the sentences about the question's things. What matched: the same circumstance (+3). The right option, 2, scored 2. · [the question and its options parsed, with trees and pragmatics](https://md.mova.elamur.ai/free/en/corpora/questions/biology/379-china-s-great-rivers-the-finless-porpoise-the-lost-baiji-chinese-alligators-and-sturgeon/t10/)

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### Test 11 · ★★ · wrong ✗ {#t11}

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Why might noisy ships harm a porpoise even if they never hit it?

- **1.** Noise makes the river water too warm — **← Mova's choice** · no support
- **2.** Porpoises hate the colour of ships — no support
- **3.** It clicks to find fish, and engine noise can drown out the echoes — **✓ the right answer** · no support
- **4.** Ships drink up the river — no support

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**Why:** No option found support in what it remembers, so it guessed: it took the first option shown. · [the question and its options parsed, with trees and pragmatics](https://md.mova.elamur.ai/free/en/corpora/questions/biology/379-china-s-great-rivers-the-finless-porpoise-the-lost-baiji-chinese-alligators-and-sturgeon/t11/)

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### Exam question 1 · formal language · wrong ✗ {#e1}

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Identify the principal method by which the baiji located its prey within the turbid waters of the Yangtze.

- **1.** By tracking the movement of birds — **← Mova's choice** · no support
- **2.** By the emission of clicks and the interpretation of returning echoes — **✓ the right answer** · no support
- **3.** By acute vision — no support
- **4.** By the sense of smell alone — no support

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**Why:** No option found support in what it remembers, so it guessed: it took the first option shown. · [the question and its options parsed, with trees and pragmatics](https://md.mova.elamur.ai/free/en/corpora/questions/biology/379-china-s-great-rivers-the-finless-porpoise-the-lost-baiji-chinese-alligators-and-sturgeon/e1/)

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### Exam question 2 · formal language · right ✓ {#e2}

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Select the response consistent with the established facts concerning the Yangtze finless porpoise.

- **1.** It is the sole porpoise of fresh water and bears a low ridge instead of a dorsal fin — **← Mova's choice** · **✓ the right answer** · score 5
- **2.** It has been extinct since 2006 — no support
- **3.** It possesses a tall dorsal fin — no support
- **4.** It inhabits the open ocean exclusively — score 1

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**Why:** It took the question to ask which statement is true. It chose option 1 with score 5, against 1 for the next best. Its support: lesson 379, line 6: «The Yangtze finless porpoise has a low ridge with tiny bumps instead of a back fin and is the only porpoise that lives in fresh water.», reached through the option's own match among the sentences about the question's things. What matched: the same circumstance (+3); the same thing acted on «only porpoise» (+2). · [the question and its options parsed, with trees and pragmatics](https://md.mova.elamur.ai/free/en/corpora/questions/biology/379-china-s-great-rivers-the-finless-porpoise-the-lost-baiji-chinese-alligators-and-sturgeon/e2/)

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### Exam question 3 · formal language · right ✓ {#e3}

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Which of the following statements most accurately characterises the number of extant species of alligator?

- **1.** Two species are extant, the American and the Chinese — **← Mova's choice** · **✓ the right answer** · score 3
- **2.** A single species is extant, namely the American — score 3
- **3.** Ten species are extant — score 3
- **4.** No species of alligator survives in the wild — score 3

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**Why:** It took the question to ask who or what does it. It chose option 1 with score 3, tied with another option at 3 (the first shown, or the one claiming less beyond what it knows, wins). Its support: lesson 372, line 2: «A hundred years ago the bison died out in the wild, and every bison alive today comes from just 12 animals kept in zoos. Bringing a species back is possible, b…», reached through the same lesson line as the sentence the question matched. What matched: it fills the role the question asks for (+2); the same doer «species» (+1). · [the question and its options parsed, with trees and pragmatics](https://md.mova.elamur.ai/free/en/corpora/questions/biology/379-china-s-great-rivers-the-finless-porpoise-the-lost-baiji-chinese-alligators-and-sturgeon/e3/)

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### Exam question 4 · formal language · right ✓ {#e4}

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Ascertain the principal cause of the decline of the Chinese sturgeon, as presented in this lesson.

- **1.** Excessive freshness of sea water at the mouth of the Yangtze — no support
- **2.** Predation by finless porpoises — no support
- **3.** Dams obstruct its access to its former spawning grounds — **← Mova's choice** · **✓ the right answer** · score 4
- **4.** A deficiency of salt in its diet — no support

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**Why:** It took the question to ask which statement is true. It chose option 3 with score 4, the only option with support. Its support: lesson 379, line 18: «Chinese sturgeon live in the sea and swim up the Yangtze to lay eggs, but dams now block their old places; in some recent years no wild breeding was seen, and…», reached through the same lesson line as the sentence the question matched. What matched: the same action «block» (+4). · [the question and its options parsed, with trees and pragmatics](https://md.mova.elamur.ai/free/en/corpora/questions/biology/379-china-s-great-rivers-the-finless-porpoise-the-lost-baiji-chinese-alligators-and-sturgeon/e4/)

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