A: Where ___ you at 8 pm on Saturday? B: I was at home watching a film.

Перевод задания: Заполните пропуски подходящими словами.

A: Where were you at 8 pm on Saturday? (Где ты был(а) в субботу в 8 вечера?)
B: I was at home watching a film. (Я был(а) дома и смотрел(а) фильм.)

Используем were с местоимением you в Past Simple.