Ответ:
1. Who is knocking at the door?
2. It is raining, take your umbrella.
3. Don't bother me, please, I am working.
4. Run downstairs, your sister is waiting for you.
5. What do you think of at this moment? [Глагол 'think' не употребляется в Continuous]
6. Let's have some tea. It is getting chilly.
7. Keep quiet, we are listening to the music.
8. "What is Tom doing now?" "He is playing the violin."
9. It is a lovely day. The sun is shining brightly.
10. What are you looking at?
Present Continuous Tense используется для указания, что действие происходит прямо сейчас.