какие времена надо поставить в предложениях: The teaching assistent ( explains/explaining)to

1. The teaching assistant is explaining - (Present Continuous - настоящее долгое время) to students how to use the new microscope.

2. What are you looking at? (Present Continuous - истинное долгое время) - The sky. It looks - (Present Simple - простое истинное время) as if its going to rain.

3. The famous opera singer is appearing (Present Continuous - истиннее долгое время) in the opera house tonight.