20. To tell you the truth, it's very hard for us to help them get rid of Internet addiction. But we _________ on this problem trying to improve the situation. A) worked B) had worked C) are working D) had been working
举一反三
- He felt very tired because he ______ 18 hours without a rest. A: had worked B: worked C: was working D: had been working
- I first met Mary three years ago when we ______ in a middle school together. A: have worked B: had been working C: were working D: had worked
- 26.Jane was tired. She__________all day. A: was working B: has worked C: worked D: had been working
- I ______ on a maths problem when he telephoned me early this morning. A: [A] had worked B: [B] was working C: [C] have worked D: [D] have been working
- All the staff of the company ________very hard last year and 15% more profit was gained. A: worked B: had worked C: have worked D: were working