Когда мы используем if что после этого используется например: if our tv set had not been out of order, we the film last night. такие варианты : а) shall watch b) would watch c) watched d) would have watched e) have watched

D) we would have watched

If our TV set had not been out of order, we would have watched the film last night.

Правила:

I тип.
Если ..., то ... | If + Present (Simple), ... will/ won't + V1
Пример:  If I have a lot of money, I would buy a car.

II тип.
Если БЫ , то БЫ ... (сейчас) | If + Past (Simple, Continuous), would / wouuldn't / could / might + V1
Пример: If I had a lot of money, I would buy a car.

III тип.
Если БЫ ..., то БЫ ... (тогда, "поезд ушел")
If + Past Perfect, I would / wouldn't have + V3
Пример:  If our TV set had not been out of order, we would have watched the film last night.

IV тип.
Если БЫ(тогда, то БЫ(сейчас) (смешанный тип)
If + Past Perfect, ... would / wouldn't / could / might + V1
Пример: If I hadn't broken my computer, I would play computer games.

Есть еще нулевой тип. Он используется, когда говорим о законах природы, расписании и т.п
Если ..., то ...
If you heat ice, it melts. (Если ты нагреваешь лёд, он тает.)