Ответ: 1. My grandparents were doctors (Мои прародители были врачами)
2. Mikhail wasn't at school yesterday (Михаил не был в школе вчера)
3. Roza was fourteen on May 1st.
4. Were you late for school?
5. They weren't very good at tennis.
6. Was your sister a student at this school?
Объяснение:
1. Используем WERE, т.к множественное число
2. WASN't, т.к ед.число
4. WERE, мн.число
5. Из-за мн.числа
6. Ед.число