Learn Hardcore French: Les élèves préparent des questions pour ces deux professions. - The students are preparing questions for these two professions.

les élèves = the students (a specific group, e.g. the students in this class, the students we’re talking about)
des élèves = (some) students (an unspecified, indefinite group)

In many teaching or classroom contexts, French naturally uses the definite article les to talk about “the students” of a class, school, etc.:

Les élèves font un exercice.
The students are doing an exercise.

Using des élèves would sound like you’re talking about just “some students” among others, not the known group of students.

Why is préparent translated as “are preparing” in English, when it looks like a simple present?

In French, the simple present (ils préparent) often covers both:

English simple present: they prepare
English present continuous: they are preparing

So:

Les élèves préparent des questions.
can mean:
- The students prepare questions (general habit)
- The students are preparing questions (right now / currently)

French does have a way to emphasize an ongoing action: être en train de + infinitive:

Les élèves sont en train de préparer des questions.
The students are in the middle of preparing questions.

But in everyday language, the plain present (préparent) is normally enough to translate as English “are preparing” when the context is current action.

Why is it des questions and not les questions or de questions?

des questions is the plural indefinite article:

une question → des questions
(a question → some questions)

Here, the students are preparing some questions, not a specific, already identified set of questions; so we use des.

les questions would mean the questions:
a particular, known set of questions (for example, questions everyone already knows about).
de questions is usually not correct alone; you’d see de instead of des when there is a plural noun preceded by an adjective:
- de bonnes questions (not des bonnes questions in standard written French)

In this sentence, questions has no adjective before it, so the normal plural indefinite article des is used: des questions.

Could we say les élèves posent des questions instead of préparent des questions? What’s the difference?

Yes, you could say les élèves posent des questions, but it changes the meaning:

préparer des questions = to prepare questions, to come up with / write down questions (before asking them)
poser des questions = to ask questions (actually saying them to someone)

In the original sentence, the focus is on the preparation stage: the students are thinking of and writing questions in advance for those two professions. If they were already asking them aloud, you’d use poser:

Les élèves posent des questions aux professionnels.
The students are asking questions to the professionals.

Why is it pour ces deux professions and not something like à ces deux professions?

The preposition pour here means for, in the sense of intended for / directed at:

préparer des questions pour quelqu’un
= to prepare questions for someone

We use:

pour to mean for (the questions are intended for those professions)
à is more often used with poser:
- poser des questions à quelqu’un
  to ask questions to someone

So:

Les élèves préparent des questions pour ces deux professions.
The students are preparing questions for these two professions.
(The questions are meant for people in those professions.)

But if we were talking about actually asking the questions, we’d say:

Les élèves posent des questions à ces deux professionnels.
The students are asking questions to these two professionals.

Why is it ces deux professions and not ces professions deux?

In French, numbers like deux, trois, quatre normally come before the noun:

deux professions, trois livres, quatre élèves

Demonstrative adjectives (ce, cet, cette, ces) also come before the noun. The usual order is:

[demonstrative] + [number] + [noun]

So:

ces deux professions = these two professions

You cannot say ces professions deux; that order is incorrect in French.

What exactly does ces mean, and how is it different from les?

ces is a demonstrative adjective (like English this/these).
les is the definite article (like English the).

ces professions = these professions (pointing to specific ones, as opposed to others)
les professions = the professions (a known group, but not “pointed at” the same way)

In the sentence pour ces deux professions, we’re clearly identifying these two particular professions that are in focus, so ces is more natural than les.

Why is professions plural and not singular like profession?

The French word professions is plural because the phrase refers to two different professions:

une profession = a profession
deux professions = two professions

Since deux is plural, the noun must also be plural:

deux professions (not deux profession)

French requires agreement in number: if the determiner is plural (deux), the noun must be plural (professions).

What’s the difference between élèves and étudiants in French?

Both can translate as students in English, but they’re not used in the same contexts:

élève: any pupil in primary school, middle school, or high school; sometimes even in certain training courses.
- les élèves du collège – the middle school students
étudiant(e): typically a student in higher education (university, grandes écoles, etc.)
- les étudiants de l’université – the university students

So les élèves here suggests school-age pupils rather than university students.

Is there any liaison or special pronunciation in Les élèves préparent des questions pour ces deux professions?

Yes, there are a few common liaisons and sound points:

Les élèves:
There is a liaison: les‿élèves → the s in les is pronounced like z:
- /lez‿elɛv/
des questions:
Usually no liaison in normal speech between des and questions.
ces deux professions:
Often a liaison between deux and professions:
- deux‿professions → /dø‿pʁɔfɛsjɔ̃/

So you might hear something like:

/lez‿elɛv pʁepaʁ dɛ kɛstjɔ̃ puʁ se dø‿pʁɔfɛsjɔ̃/

Could the sentence also be Les élèves préparent des questions sur ces deux professions? What would change?

Yes, you can say:

Les élèves préparent des questions sur ces deux professions.

With sur, the nuance is:

des questions sur X = questions about X

So:

pour ces deux professions suggests the questions are for (to be asked to) people in those professions.
sur ces deux professions suggests the questions are about those professions as a topic (not necessarily directed to people who do those jobs).

Depending on the context, both can be correct, but the focus changes slightly.

How would the sentence change if there was only one profession?

With just one profession, you’d make the demonstrative and the noun singular:

Les élèves préparent des questions pour cette profession.
The students are preparing questions for this profession.

Changes:

ces → cette (feminine singular for profession)
deux professions → profession (no number word, and the noun becomes singular)