Imparfait versus Passé Composé

Question

Why is the phrase "notre prof de science nous demandait de préparer ..." in imparfait not passé composé? Since the requests occurred at specific points in time I thought it would be passé composé. Is it because the requests were repeated each year?

Accepted Answer

Hi J, 
You have answered your own question.
This is a classic case of repetition, almost a habit.
It could have been translated -
Each year, our science teacher would ask us to prepare 
If you need a refresher take a look at the following lesson which deals with this topic-
Expressing past habits or repeated actions with the imperfect tense in French (L'Imparfait)
Bonne Continuation !