---
title: Identify the two substances whose simultaneous presence is required… — Rust: iron's slow fire · tree and pragmatics
description: Identify the two substances whose simultaneous presence is required for the rusting of iron. Exam question 1 of lesson 13 «Rust: iron's slow fire» of the chemistry course of Mova's primary school, with the dependency tree and pragmatics of the question and of each option; Mova's choice was wrong.
---

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# Exam question 1 · Rust: iron's slow fire

<!-- .ven lang=en -->
Identify the two substances whose simultaneous presence is required for the rusting of iron.

<!-- .vintro -->
**Mova's choice:** option 1 · **The right answer:** option 2 · wrong ✗ · **Who acts:** you · **What happens:** identify, require · **To what, where:** two substances, simultaneous presence

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This is exam question 1 of lesson 13 «Rust: iron's slow fire» of the chemistry 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/chemistry/13-rust-irons-slow-fire/#e1).

## The question {#question}

```conllu
# sent_id = question:chemistry:13-rust-irons-slow-fire:e1:1
# text = Identify the two substances whose simultaneous presence is required for the rusting of iron.
1	Identify	identify	VERB	VB	Mood=Imp|VerbForm=Fin	0	root	_	_
2	the	the	DET	DT	Definite=Def|PronType=Art	4	det	_	_
3	two	two	NUM	CD	NumForm=Word|NumType=Card	4	nummod	_	_
4	substances	substance	NOUN	NNS	Number=Plur	1	obj	_	_
5	whose	whose	PRON	WP$	Poss=Yes|PronType=Rel	7	nmod:poss	_	_
6	simultaneous	simultaneous	ADJ	JJ	Degree=Pos	7	amod	_	_
7	presence	presence	NOUN	NN	Number=Sing	9	nsubj:pass	_	_
8	is	be	AUX	VBZ	Mood=Ind|Number=Sing|Person=3|Tense=Pres|VerbForm=Fin	9	aux:pass	_	_
9	required	require	VERB	VBN	Tense=Past|VerbForm=Part|Voice=Pass	4	acl:relcl	_	_
10	for	for	ADP	IN	_	12	case	_	_
11	the	the	DET	DT	Definite=Def|PronType=Art	12	det	_	_
12	rusting	rusting	NOUN	NN	Number=Sing	9	obl	_	_
13	of	of	ADP	IN	_	14	case	_	_
14	iron	iron	NOUN	NN	Number=Sing	12	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 two substances |  |  |  |  | vn characterize-29.2-1-1 «NP V NP S\_ING»: agent=Agent substance=Theme |
| 2 | **require** | present · passive |  | simultaneous presence |  |  |  | for the rusting of iron | vn require-103-1 «NP V NP»: subject=Precondition |

<!-- .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 {#o1}

<!-- .ven lang=en -->
Carbon and sunlight

```conllu
# sent_id = question:chemistry:13-rust-irons-slow-fire:e1:o1:1
# text = Carbon and sunlight
1	Carbon	carbon	NOUN	NN	Number=Sing	0	root	_	_
2	and	and	CCONJ	CC	_	3	cc	_	_
3	sunlight	sunlight	NOUN	NN	Number=Sing	1	conj	_	_
```

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

### Option 2 · ✓ the right answer {#o2}

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

```conllu
# sent_id = question:chemistry:13-rust-irons-slow-fire:e1:o2:1
# text = Oxygen and water
1	Oxygen	oxygen	NOUN	NN	Number=Sing	0	root	_	_
2	and	and	CCONJ	CC	_	3	cc	_	_
3	water	water	NOUN	NN	Number=Sing	1	conj	_	_
```

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

### Option 3 {#o3}

<!-- .ven lang=en -->
Oxygen and sea salt

```conllu
# sent_id = question:chemistry:13-rust-irons-slow-fire:e1:o3:1
# text = Oxygen and sea salt
1	Oxygen	oxygen	NOUN	NN	Number=Sing	0	root	_	_
2	and	and	CCONJ	CC	_	4	cc	_	_
3	sea	sea	NOUN	NN	Number=Sing	4	compound	_	_
4	salt	salt	NOUN	NN	Number=Sing	1	conj	_	_
```

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

### Option 4 {#o4}

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

```conllu
# sent_id = question:chemistry:13-rust-irons-slow-fire:e1:o4:1
# text = Nitrogen and water
1	Nitrogen	Nitrogen	PROPN	NNP	Number=Sing	0	root	_	_
2	and	and	CCONJ	CC	_	3	cc	_	_
3	water	water	NOUN	NN	Number=Sing	1	conj	_	_
```

<!-- .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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