I'm reading "Assimil New French with Ease", and in lesson 90 it goes:
Quand le Tour de France a-t-il été créé?
Combien y avait-il d'étapes à l'origine?
Combien y en a-t-il aujourd'hui?
Dans quels pays les coureurs se rendent-ils ?
Now I don't understand, why we need an "ils" in the last line? The question means
To (in) which countries do the racers go?
To which countries is the Dans quels pays, why there is still an ils at the end of the line?
When you ask a question, you need to inverse the subject ("ils") and the verb ("rendent").
In this sentence, the verb is "rendre":
Dans quels pays les coureurs se rendent-ils ?
Another example:
Je vais à Paris. (I'm going to Paris)
Vais-je à Paris ? (Am I going to Paris ?)
Another tip: In some cases, you will have to add a "t" between the subject and the verb, except if your verb already finish by a "t", or a "d":
aime-t-il ?
parle-t-elle ?
Sait-il ?
Prend-on ?
More info: https://www.lawlessfrench.com/grammar/euphonic-inversion/
