Ответ:
1. My brother has been playing...
2. How long has it been snowing?
3. I've been trying to find my documents...
4. My sister hasn't been sending job applications...
5. How has he been reading this book?
6. He has been taking his medicine...
7. How long have you been learning English?
8. Since when have they been working on the project?
9. I have been working too hard...
10. The vegetables have been boiling since 10 o'clock.