---
title: Which gas do both a candle flame and a person need? — Air and why we need it · tree and pragmatics
description: Which gas do both a candle flame and a person need? Test 8 · ★ of lesson 17 «Air and why we need it» of the world course of Mova's primary school, with the dependency tree and pragmatics of the question and of each option; Mova's choice was right.
---

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# Test 8 · ★ · Air and why we need it

<!-- .ven lang=en -->
Which gas do both a candle flame and a person need?

<!-- .vintro -->
**Mova's choice:** option 4 · **The right answer:** option 4 · right ✓ · **Who acts:** gas, you · **What happens:** do, need · **To what, where:** candle flame

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This is test 8 · ★ of lesson 17 «Air and why we need it» of the world course of Mova's primary school. 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/world/17-air-oxygen-carbon-dioxide/#t8).

## The question {#question}

```conllu
# sent_id = question:world:17-air-oxygen-carbon-dioxide:t8:1
# text = Which gas do both a candle flame and a person need?
1	Which	which	PRON	WDT	PronType=Rel	3	obj	_	_
2	gas	gas	NOUN	NN	Number=Sing	3	nsubj	_	_
3	do	do	VERB	VBP	Mood=Ind|Number=Plur|Person=3|Tense=Pres|VerbForm=Fin	11	advcl	_	_
4	both	both	CCONJ	CC	_	7	cc:preconj	_	_
5	a	a	DET	DT	Definite=Ind|PronType=Art	7	det	_	_
6	candle	candle	NOUN	NN	Number=Sing	7	compound	_	_
7	flame	flame	NOUN	NN	Number=Sing	3	obj	_	_
8	and	and	CCONJ	CC	_	10	cc	_	_
9	a	a	DET	DT	Definite=Ind|PronType=Art	10	det	_	_
10	person	person	NOUN	NN	Number=Sing	7	conj	_	_
11	need	need	VERB	VB	Mood=Imp|VerbForm=Fin	0	root	_	SpaceAfter=No
12	?	?	PUNCT	.	_	11	punct	_	_
```

<!-- .fr -->
| # | verb | tense, mood | who | what, whom | to whom | where | when | other | roles by |
| --- | --- | --- | --- | --- | --- | --- | --- | --- | --- |
| 1 | **do** | present | gas | a candle flame and a person |  |  |  |  | tree rules |
| 2 | **need** | imperative | you *not said here* |  |  |  |  |  | vn want-32.1-1-1 «NP V NP S\_INF»: agent=Pivot |

<!-- .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 {#o1}

<!-- .ven lang=en -->
Nitrogen

```conllu
# sent_id = question:world:17-air-oxygen-carbon-dioxide:t8:o1:1
# text = Nitrogen
1	Nitrogen	Nitrogen	PROPN	NNP	Number=Sing	0	root	_	_
```

<!-- .note -->
The frames reader finds no event or fact in this sentence.

### Option 2 {#o2}

<!-- .ven lang=en -->
Helium

```conllu
# sent_id = question:world:17-air-oxygen-carbon-dioxide:t8:o2:1
# text = Helium
1	Helium	helium	NOUN	NN	Number=Sing	0	root	_	_
```

<!-- .note -->
The frames reader finds no event or fact in this sentence.

### Option 3 {#o3}

<!-- .ven lang=en -->
Carbon dioxide

```conllu
# sent_id = question:world:17-air-oxygen-carbon-dioxide:t8:o3:1
# text = Carbon dioxide
1	Carbon	carbon	NOUN	NN	Number=Sing	2	compound	_	_
2	dioxide	dioxide	NOUN	NN	Number=Sing	0	root	_	_
```

<!-- .note -->
The frames reader finds no event or fact in this sentence.

### Option 4 · ← Mova's choice · ✓ the right answer {#o4}

<!-- .ven lang=en -->
Oxygen

```conllu
# sent_id = question:world:17-air-oxygen-carbon-dioxide:t8:o4:1
# text = Oxygen
1	Oxygen	oxygen	NOUN	NN	Number=Sing	0	root	_	_
```

<!-- .note -->
The frames reader finds no event or fact in this sentence.

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**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.

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- ← previous: [Air and why we need it, test 7](https://md.mova.elamur.ai/free/en/corpora/questions/world/17-air-oxygen-carbon-dioxide/t7/)
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