Le choix est difficile parce que tous les livres sont intéressants.

Because choix is a masculine noun in French, so it takes le in the singular.

• le choix = the choice
• un choix = a choice

French noun gender is grammatical, so you usually need to learn it with each noun.

Choix means choice or selection. In this sentence, Le choix est difficile means that choosing is hard because there are many good options.

It is singular because the sentence is talking about the overall choice to be made, not several separate choices.

Choix is pronounced roughly like shwah.

The ch sounds like sh, and the final x is silent.

Yes. They come from the same word family:

• choisir = to choose
• le choix = the choice

This is a very common pattern in French: a verb and a related noun often look different, so it is worth learning them together.

Est is the he/she/it form of être, which means to be.

So:

• le choix est difficile = the choice is difficult

French uses être here just as English uses to be.

It actually already matches the subject correctly.

Difficile is an adjective, and adjectives usually agree with the noun they describe. But difficile has the same form in masculine singular and feminine singular:

• un choix difficile
• une décision difficile

Only the plural changes in spelling:

• des choix difficiles

So in this sentence, difficile is singular because le choix is singular.

Parce que means because. It introduces the reason:

• Le choix est difficile = the choice is difficult
• parce que tous les livres sont intéressants = because all the books are interesting

It is one of the most common ways to give a reason in everyday French.

Yes, you could say:

• Le choix est difficile car tous les livres sont intéressants.

That is also correct. But parce que is more common in everyday speech. Car often sounds a little more formal or written.

In normal modern French, tous usually needs an article before the noun here:

• tous les livres = all the books

So the pattern is:

• tous les
  • masculine plural noun
• toutes les
  • feminine plural noun

Saying tous livres would sound unnatural in ordinary French.

Because livre is a masculine noun.

• le livre
• les livres

So the correct plural form is:

• tous les livres = all the books

If the noun were feminine, you would use toutes:

• toutes les pages = all the pages

Because the subject is tous les livres, which is plural.

That means:

• the verb must be plural: sont
• the adjective must also be plural: intéressants

Compare:

• Le livre est intéressant.
• Les livres sont intéressants.

The s marks the plural. It agrees with livres, which is masculine plural.

So:

• intéressant = masculine singular
• intéressants = masculine plural
• intéressante = feminine singular
• intéressantes = feminine plural

Usually, no. In standard French, intéressant and intéressants are pronounced the same.

The final s in intéressants is normally silent.

So the difference is mainly in spelling, not pronunciation.

Yes.

Some silent letters:

• choix: the final x is silent
• livres: the final s is silent
• intéressants: the final s is silent

An important liaison:

• sont intéressants is pronounced with a liaison between sont and intéressants

So it sounds like son-tintéressants, with a t sound linking the words.

Yes. You can also say:

• Parce que tous les livres sont intéressants, le choix est difficile.

This means the same thing, but the emphasis changes slightly. Putting the parce que clause first highlights the reason before giving the result.

In writing, a comma is normally used when that clause comes first.

A rough pronunciation guide is:

luh shwah eh dee-fee-seel parskuh too lay leevr son-tay(n)-tay-ray-san

A more accurate IPA version is:

lə ʃwa ɛ di.fi.sil paʁs kə tu le livʁ sɔ̃.t‿ɛ̃.te.ʁe.sɑ̃

The most important things to notice are:

• choix = shwah
• tous here sounds like too
• sont intéressants has a liaison between the two words