Поставьте предложения в вопросительную и отрицательную формы.
1.Our engineer will be busy tomorrow.
2.The classes are over at 4 o'clock.
3.Your friend is fond of music.
4.They were absent yesterday.

В первом случае просто ставишь глагол на первое место1. Will our engineer be busy tomorrow?2. Are the classes over at 4 o'clock?3. Is your friend fond of music?4. Were they absent yesterday?А во втором добавляешь к глаголу частичку not1. Our engineer won't be busy tomorrow2. The classes aren't over at 4 o'clock3. Your friend isn't fond music4. They weren't absent yesterday