Questions & Answers about J'ai vu que le chien avait déchiré le siège.
Why do we use avait déchiré instead of the passé composé (a déchiré)?
Avait déchiré is in the Plus-que-parfait (the "had done" tense). We use it here to show that the dog tearing the seat happened before the other past action in the sentence (j'ai vu - I saw).
How do you form the Plus-que-parfait tense in this sentence?
What would happen to the meaning if I used the imparfait (déchirait) instead?
What kind of seat is a siège? Could I use chaise here instead?
Chaise usually refers to a basic, hard chair (like a wooden dining chair). Siège is a broader term for anything you sit on, such as a car seat, an airplane seat, or a cushioned armchair. Since the dog "tore" (a déchiré) it, it implies there was fabric or leather involved, making siège a very natural fit.