1. The teaching assistent is explaining to students how to
use the new microscope. (Pr. Contin.)
2. What are you looking at? (Pr. Continuous)-The sky.It looks (Pr. Simple) as if its
going to rain.
3. The famous opera singer (apptar) ft opera house tonight - Здесь у вас ошибка в написании глагола. Скорее всего, здесь будет is appearing (Pr. Cont)