What construction is being used to ask the question "Que lisent les enfants?" ?

Question

Duolingo had the following sentence:

Que lisent les enfants?

I do not understand the construction being used here.

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I understand that one way to construct some types of questions is to use an interrogative pronoun. My understanding of how to use "qui" and "que" comes from this page from the University of Texas French Grammar website: https://www.laits.utexas.edu/tex/gr/int5.html. I've read that page carefully and I think I understand it all.

I've learned (from a different source) to become familiar with constructing a question using an interrogative pronoun, by first taking a sentence that might be an answer to the question, and then converting that "answer" to a question by replacing a subject (or object) with an interrogative pronoun.

My construction rule is as follows: I first ask myself "is the noun getting replaced a human or animal, or is it an inanimate thing? In the first case, look at the "qui" section of the webpage I linked to. In the second case, look at the "que" section". I next ask myself, "Is the noun the subject, or the object, of the sentence?". The final step is to start the sentence with the correct interrogative pronoun, and then write the rest of the sentence afterwards (except the noun that is getting replaced by the pronoun).

example:

J'adore les pommes.
-->
Qu'est-ce que tu adores ?
(ie Qu'est-ce que = a "que" (ie inanimate) interrogative pronoun, used to replace a direct object)

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I can't see how to construct the question "Que lisent les enfants" using these rules, however. "Que" as an interrogative pronoun, according to the website I linked, is short for only "Qu'est-ce que" (ie inanimate, direct object).

But then the sentence doesn't have a subject noun for the verb "lisent"! and also, "lisent" would have two direct objects: "les enfants" and whatever noun "Que" is replacing!

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My question: what is the "construction rule" being used to construct this sentence?

It seems that it starts with "Qu'est-ce que les enfants lisent", and switches the subject and verb: "Qu'est-ce que lisent les enfants" (or "Que lisent les enfants" for short). Can I do this with ALL the seven interrogative pronouns (qui, qui est-ce qui, qui est-ce que, que, qu'est-ce que, qu'est-ce qui, quoi) listed on that website? (For example, may I turn "Qui est-ce qui achète ces pommes ?" into the equivalent sentence: "Qui est-ce qui ces pommes achète ?")

Answer 1

It's inversion. Instead of saying Les enfants lisent quoi (the normal subject-verb-object word order), the subject and verb have changed places, and the object precedes them. And then, because quoi is used only after a verb, it reverts back to its "normal" form que as an interrogative pronoun.

Answer 2

Building inversion

lkl's answer is right about inversion. I however find his answer about when you can use inversion unclear, so I'll complete here.

First off, inversion is a more compact form, but using est-ce is the standard in spoken language. First off, how is it built:

Qu'est-ce que les enfants lisent ?
Que lisent les enfants ?

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Qu'est-ce que c'est ?
Qu'est-ce ?

As you can see, you can:

• either use the affirmative structure, preceding it with qu'est-ce que;
• or use only que and move the verb before the subject.

This is applicable only when que is not the subject of the question.

When the interrogative pronoun is subject: no inversion

Qui est-ce qui achète ces pommes ?
Qui achète ces pommes ?

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Qui est-ce qui a fait ça ?
Qui a fait ça ?

There is no inversion here.

You can remove the est-ce qui in this case. The intonation becomes important here, since there is no difference between the question and an affirmative subordinate clause.

There is some similarity with the other answer I gave you about how to choose the pronoun (qui/que) according to whether it is subject or not.

Other pronouns

I can't think of a structure using another pronoun than qui and que which could lead to this kind of construction duality. This is deeply linked with the qu* est-ce qu*, which works only with qui and que.