현재완료와 현재진행형 문제 질문

현재진행형 단원인데 관련 없는 문제도 있는 것 같아요.
1. What they ( ) so far is using sea water as a source of electricity.
A. do B. had been doing C. have been doing D. did
2. They ( ) their classroom. It looks completely new again.
A. have redecorated B. were redecorated C. were redecorating D. will redecorate
3. She used to complain about everything but now she ( ) a lot.
A. changed B. had changed C. has changed D. had been changing
4. “쟤는 만날 수업 시간에 잠만 자.”를 is와 sleep을 활용해 영어로 어떻게 쓰나요?