21. she has been standing
22. has been standing
23. I have spent a lot of time travelling since I got this new job.
24. When I was at school, we had all been studying Latin. (preferably: we were all studying Latin)
25. After he had finished breakfast, he sat down to write some letters.
26. When I met him, he had been working as a waiter...
27. I've never learnt to ski.
28. Have you finished with the ....
29. We had been living in Schotland until I was eighteen. (preferably: We lived in Schotland until I was eighteen.)
30. She has been having a hard life, ....