Excusez-moi, madame, est-ce que ces navets sont plus frais que ceux de la semaine dernière?

Excusez-moi uses the vous form, so it is formal or polite. Since the speaker is addressing madame, that level of politeness makes sense.

• Excuse-moi = excuse me, addressed to one person informally
• Excusez-moi = excuse me, addressed to one person formally or more than one person

This is the imperative of excuser.

Madame is a polite way to address the woman directly, similar to ma’am in English. It helps make the sentence sound courteous in a shop or market.

So the sentence structure is roughly:

• Excusez-moi = Excuse me
• madame = ma’am
• then the actual question follows

Est-ce que is a very common way to turn a statement into a yes/no question.

Without it, the statement would be:

• Ces navets sont plus frais que ceux de la semaine dernière. = These turnips are fresher than last week’s.

With est-ce que, it becomes a question:

• Est-ce que ces navets sont plus frais que ceux de la semaine dernière ? = Are these turnips fresher than last week’s?

It does not translate word-for-word naturally into English; it is mainly a question marker.

No. Est-ce que is a fixed expression and does not agree with the subject.

Even if the subject is plural, you still say:

• Est-ce que ces navets... ?
• Est-ce que les pommes... ?
• Est-ce qu’ils... ?

So the plural subject ces navets does not change est-ce que.

Ces means these. It points to specific turnips, probably the ones the speaker is looking at right now.

• ces navets = these turnips
• les navets = the turnips
• des navets = some turnips

Since the sentence compares the turnips in front of the speaker with those from last week, ces is the natural choice.

Ceux means those ones and replaces a repeated masculine plural noun.

In full, the idea is:

• ...plus frais que les navets de la semaine dernière

But French often avoids repetition by using ceux:

• ...plus frais que ceux de la semaine dernière

Because navets is masculine plural, the correct pronoun is ceux.

Related forms are:

• celui = that one / the one, masculine singular
• celle = that one / the one, feminine singular
• ceux = those / the ones, masculine plural
• celles = those / the ones, feminine plural

Adjectives in French agree with the noun they describe.

Here, frais describes navets, and navets is:

• masculine
• plural

So the correct form is frais.

Compare:

• un navet frais = a fresh turnip
• des navets frais = fresh turnips
• une pomme fraîche = a fresh apple
• des pommes fraîches = fresh apples

So fraîches would be used with a feminine plural noun, not with navets.

This is the standard French pattern for a comparative of superiority:

• plus + adjective + que
• more + adjective + than

So:

• plus frais que = fresher than

Other examples:

• plus grand que = taller/bigger than
• plus cher que = more expensive than
• plus rapide que = faster than

Here the comparison is between:

• ces navets
  and
• ceux de la semaine dernière

Because ceux needs a complement to say those of/from ...

So:

• ceux de la semaine dernière = those from last week / last week’s ones

The de links ceux to the time expression.

Compare:

• ceux du marché = the ones from the market
• ceux de ma sœur = my sister’s ones / my sister’s
• ceux de la semaine dernière = last week’s ones

Yes. French has more than one way to ask a yes/no question.

For example:

• Ces navets sont plus frais que ceux de la semaine dernière ?
  This uses rising intonation and is common in speech.

• Ces navets sont-ils plus frais que ceux de la semaine dernière ?
  This uses inversion and is more formal or written.

• Est-ce que ces navets sont plus frais que ceux de la semaine dernière ?
  This is very standard and natural.

So the version in the sentence is polite, clear, and very common.

The final -s in navets is normally not pronounced.

So navets sounds roughly like nah-vay.

A few pronunciation notes:

• Excusez-moi → the z is pronounced
• est-ce que → often sounds compact in speech
• ces navets sont → there is a liaison possibility before sont, so connected speech may sound smoother than the spelling suggests
• frais is pronounced roughly like fray

• ceux is pronounced roughly like suh or seu

  French spelling and pronunciation do not always match in an obvious way, so this is a very normal learner question.

Yes, you can repeat the noun, and French speakers would understand you:

• ...plus frais que les navets de la semaine dernière

But using ceux sounds more natural and less repetitive. French often prefers pronouns like celui / celle / ceux / celles when the noun has already been mentioned.

So:

• ...que les navets de la semaine dernière = correct
• ...que ceux de la semaine dernière = more elegant and more natural in many contexts

Yes. Dernière means last, and it agrees with semaine, which is feminine singular.

So:

• la semaine dernière = last week

Compare:

• le mois dernier = last month
• l’année dernière = last year
• les semaines dernières = the last weeks

The form changes depending on the noun it describes.