French language Q&A Forum

Is it that pronom 'où' is followed by a noun or subject pronoun?

As seen in above examples.

Thanks a lot 

why not Olivier arrive á la piscine

In this example why is the verb to be present?  Elle est assise au coin de la cheminée.

J'adore les bonbons ! - Oui, mais lesquels sont tes préférés ?

In this example can’t the answer be as-

‘Oui,mais lequel est ton préféré?’

How to judge whether the answer of lesquelles or lequel should be singular or plural ?

Pls confirm 

Thnx a lot