---
title: Identify the principal reason for which food chains are seldom longe… — Food chains: sun, plants, plant-eaters… · tree and pragmatics
description: Identify the principal reason for which food chains are seldom longer than five steps. Exam question 2 of lesson 46 «Food chains: sun, plants, plant-eaters, meat-eaters» of the biology course of Mova's primary school, with the dependency tree and pragmatics of the question and of each option; Mova's
---

<!-- md -->
[Mova](https://md.mova.elamur.ai/free/en/) · [this page in HTML](https://mova.elamur.ai/free/en/corpora/questions/biology/46-food-chains/e2/)

<!-- crumbs -->
[home](https://md.mova.elamur.ai/free/en/) / [corpora](https://md.mova.elamur.ai/free/en/corpora/) / [questions](https://md.mova.elamur.ai/free/en/corpora/questions/) / [Biology](https://md.mova.elamur.ai/free/en/corpora/questions/biology/) / [Food chains: sun, plants, plant-eaters…](https://md.mova.elamur.ai/free/en/corpora/questions/biology/46-food-chains/) / e2

# Exam question 2 · Food chains: sun, plants, plant-eaters, meat-eaters

<!-- .ven lang=en -->
Identify the principal reason for which food chains are seldom longer than five steps.

<!-- .vintro -->
**Mova's choice:** option 1 · **The right answer:** option 1 · right ✓ · **Who acts:** you, food chains · **What happens:** identify, be · **To what, where:** principal reason

<!-- .vabout -->
This is exam question 2 of lesson 46 «Food chains: sun, plants, plant-eaters, meat-eaters» of the biology course of Mova's primary school, asked in stiff, formal language. The page gives the question's syntax tree — a dependency tree in the style of Universal Dependencies — and its pragmatics clause by clause, then the 4 options as the student saw them, each with its tree and pragmatics. Every text is parsed by Mova itself. How the student answered it, with the score of every option and why: [the test at school](https://md.mova.elamur.ai/free/en/school-run/biology/46-food-chains/#e2).

## The question {#question}

```conllu
# sent_id = question:biology:46-food-chains:e2:1
# text = Identify the principal reason for which food chains are seldom longer than five steps.
1	Identify	identify	VERB	VB	Mood=Imp|VerbForm=Fin	0	root	_	_
2	the	the	DET	DT	Definite=Def|PronType=Art	4	det	_	_
3	principal	principal	ADJ	JJ	Degree=Pos	4	amod	_	_
4	reason	reason	NOUN	NN	Number=Sing	1	obj	_	_
5	for	for	ADP	IN	_	6	case	_	_
6	which	which	DET	WDT	PronType=Int	8	det	_	_
7	food	food	NOUN	NN	Number=Sing	8	compound	_	_
8	chains	chain	NOUN	NNS	Number=Plur	14	nsubj	_	_
9	are	be	AUX	VBP	Mood=Ind|Number=Plur|Person=3|Tense=Pres|VerbForm=Fin	14	cop	_	_
10	seldom	seldom	ADV	RB	_	11	advmod	_	_
11	longer	long	ADV	RBR	Degree=Cmp	14	advmod	_	_
12	than	than	ADP	IN	_	14	case	_	_
13	five	five	NUM	CD	NumForm=Word|NumType=Card	14	nummod	_	_
14	steps	step	NOUN	NNS	Number=Plur	4	nmod	_	SpaceAfter=No
15	.	.	PUNCT	.	_	1	punct	_	_
```

<!-- .fr -->
| # | verb | tense, mood | who | what, whom | to whom | where | when | other | roles by |
| --- | --- | --- | --- | --- | --- | --- | --- | --- | --- |
| 1 | **identify** | imperative | you *not said here* | the principal reason |  |  |  |  | vn characterize-29.2-1-1 «NP V NP S\_ING»: agent=Agent reason=Theme |
| 2 | **is** | present | which food chains |  |  |  |  | than five steps; long *property* | tree rules |

<!-- .note -->
One row per clause the reader finds. «not said here»: a role filled from the clause above. «roles by»: a VerbNet class and frame when one fits the verb, else the reader's rules on the tree.

## The options {#options}

### Option 1 · ← Mova's choice · ✓ the right answer {#o1}

<!-- .ven lang=en -->
At each step most energy is expended, so too little remains for further steps

<!-- fold The tree, 14 words -->
```conllu
# sent_id = question:biology:46-food-chains:e2:o1:1
# text = At each step most energy is expended, so too little remains for further steps
1	At	at	ADP	IN	_	3	case	_	_
2	each	each	DET	DT	PronType=Tot	3	det	_	_
3	step	step	NOUN	NN	Number=Sing	7	obl	_	_
4	most	most	ADJ	JJS	Degree=Sup	5	amod	_	_
5	energy	energy	NOUN	NN	Number=Sing	7	nsubj:pass	_	_
6	is	be	AUX	VBZ	Mood=Ind|Number=Sing|Person=3|Tense=Pres|VerbForm=Fin	7	aux:pass	_	_
7	expended	expend	VERB	VBN	Tense=Past|VerbForm=Part|Voice=Pass	0	root	_	SpaceAfter=No
8	,	,	PUNCT	,	_	12	punct	_	_
9	so	so	ADV	RB	_	12	advmod	_	_
10	too	too	ADV	RB	_	11	advmod	_	_
11	little	little	ADJ	JJ	Degree=Pos	12	amod	_	_
12	remains	remains	NOUN	NNS	Number=Ptan	7	obl	_	_
13	for	for	ADP	IN	_	15	case	_	_
14	further	further	ADJ	JJ	Degree=Pos	15	amod	_	_
15	steps	step	NOUN	NNS	Number=Plur	7	obl	_	_
```

<!-- .fr -->
| # | verb | tense, mood | who | what, whom | to whom | where | when | other | roles by |
| --- | --- | --- | --- | --- | --- | --- | --- | --- | --- |
| 1 | **expend** | present · passive |  | most energy |  |  |  | at each step; for further steps; little remains *obl* | tree rules |

### Option 2 {#o2}

<!-- .ven lang=en -->
Plants cease to grow when a chain exceeds five steps

```conllu
# sent_id = question:biology:46-food-chains:e2:o2:1
# text = Plants cease to grow when a chain exceeds five steps
1	Plants	plant	NOUN	NNS	Number=Plur	2	nsubj	_	_
2	cease	cease	VERB	VBP	Mood=Ind|Number=Plur|Person=3|Tense=Pres|VerbForm=Fin	0	root	_	_
3	to	to	PART	TO	_	4	mark	_	_
4	grow	grow	VERB	VB	VerbForm=Inf	2	xcomp	_	_
5	when	when	SCONJ	WRB	_	8	mark	_	_
6	a	a	DET	DT	Definite=Ind|PronType=Art	7	det	_	_
7	chain	chain	NOUN	NN	Number=Sing	8	nsubj	_	_
8	exceeds	exceed	VERB	VBZ	Mood=Ind|Number=Sing|Person=3|Tense=Pres|VerbForm=Fin	4	advcl	_	_
9	five	five	NUM	CD	NumForm=Word|NumType=Card	10	nummod	_	_
10	steps	step	NOUN	NNS	Number=Plur	8	obj	_	_
```

<!-- .fr -->
| # | verb | tense, mood | who | what, whom | to whom | where | when | other | roles by |
| --- | --- | --- | --- | --- | --- | --- | --- | --- | --- |
| 1 | **cease** | present | Plants |  |  |  |  |  | vn stop-55.4-1-1 «NP V S\_ING»: agent=Affector clause=Eventuality |
| 2 | **grow** | to-infinitive | Plants *not said here* |  |  |  |  |  | vn appear-48.1.1 «NP V»: agent=Theme |
| 3 | **exceed** | present | a chain | five steps |  |  |  |  | vn exceed-90 «NP V NP»: agent=Pivot step=Theme |

### Option 3 {#o3}

<!-- .ven lang=en -->
Predators are prohibited by their nature from consuming other predators

```conllu
# sent_id = question:biology:46-food-chains:e2:o3:1
# text = Predators are prohibited by their nature from consuming other predators
1	Predators	predator	NOUN	NNS	Number=Plur	3	nsubj:pass	_	_
2	are	be	AUX	VBP	Mood=Ind|Number=Plur|Person=3|Tense=Pres|VerbForm=Fin	3	aux:pass	_	_
3	prohibited	prohibit	VERB	VBN	Tense=Past|VerbForm=Part|Voice=Pass	0	root	_	_
4	by	by	ADP	IN	_	6	case	_	_
5	their	their	PRON	PRP$	Case=Gen|Number=Plur|Person=3|Poss=Yes|PronType=Prs	6	nmod:poss	_	_
6	nature	nature	NOUN	NN	Number=Sing	3	obl	_	_
7	from	from	SCONJ	IN	_	8	mark	_	_
8	consuming	consume	VERB	VBG	Tense=Pres|VerbForm=Part	3	advcl	_	_
9	other	other	ADJ	JJ	Degree=Pos	10	amod	_	_
10	predators	predator	NOUN	NNS	Number=Plur	8	obj	_	_
```

<!-- .fr -->
| # | verb | tense, mood | who | what, whom | to whom | where | when | other | roles by |
| --- | --- | --- | --- | --- | --- | --- | --- | --- | --- |
| 1 | **prohibit** | present · passive | Predators's nature | Predators |  |  |  |  | vn forbid-64.4-1 «NP V NP»: agent=Causer subject=Theme |
| 2 | **consume** | gerund | Predators's nature *not said here* | other predators |  |  |  |  | vn consume-66 «NP V NP»: agent=Agent predator=Asset |

### Option 4 {#o4}

<!-- .ven lang=en -->
Animals at the summit of a chain require no food

```conllu
# sent_id = question:biology:46-food-chains:e2:o4:1
# text = Animals at the summit of a chain require no food
1	Animals	animal	NOUN	NNS	Number=Plur	8	nsubj	_	_
2	at	at	ADP	IN	_	4	case	_	_
3	the	the	DET	DT	Definite=Def|PronType=Art	4	det	_	_
4	summit	summit	NOUN	NN	Number=Sing	1	nmod	_	_
5	of	of	ADP	IN	_	7	case	_	_
6	a	a	DET	DT	Definite=Ind|PronType=Art	7	det	_	_
7	chain	chain	NOUN	NN	Number=Sing	4	nmod	_	_
8	require	require	VERB	VBP	Mood=Ind|Number=Plur|Person=3|Tense=Pres|VerbForm=Fin	0	root	_	_
9	no	no	DET	DT	PronType=Neg	10	det	_	_
10	food	food	NOUN	NN	Number=Sing	8	obj	_	_
```

<!-- .fr -->
| # | verb | tense, mood | who | what, whom | to whom | where | when | other | roles by |
| --- | --- | --- | --- | --- | --- | --- | --- | --- | --- |
| 1 | **require** | present | Animals at the summit of a chain | no food |  |  |  |  | vn require-103-1 «NP V NP»: agent=Theme food=Precondition |

<!-- div src -->

**Text:** the tests of Mova's primary school, written for Mova (`world/data/school/`), as the course runner gave them to the student. **Trees:** Mova's own parse — the `en` model on the CPU, when the site is built — not checked by a teacher; they may be wrong. **Frames:** Mova's frames reader (`prag`), each text read on its own. Elamur Cosmic License.

<!-- /div -->

<!-- pn -->
- ← previous: [Food chains: sun, plants, plant-eaters…, exam 1](https://md.mova.elamur.ai/free/en/corpora/questions/biology/46-food-chains/e1/)
- next →: [Food chains: sun, plants, plant-eaters…, exam 3](https://md.mova.elamur.ai/free/en/corpora/questions/biology/46-food-chains/e3/)
- ↑ back to [Food chains: sun, plants, plant-eaters, meat-eaters](https://md.mova.elamur.ai/free/en/corpora/questions/biology/46-food-chains/)