A: Did Dan come to school yesterday? B: No because he was ill. (Прошедшее время, так как речь идет о вчерашнем дне).
A: Do you often cook at home? B: No I don't but today I am cooking (cook) for my parents. (Present Continuous, так как действие происходит сейчас).
A: Where did you spend your summer holidays last year? B: I went (go) to France in June and I travelled (travel) to Spain in July. (Прошедшее время, так как речь идет о прошлом лете).
They always do (do) their shopping on Saturday morning but today they are staying (stay) at home because they are not feeling (not/feel) very well. (Present Simple для обычного действия, Present Continuous для действия, происходящего сейчас).