8. Although the causes of cancer _____, we do not yet have any practical way to prevent it.
A: A. are being uncovered
B: B. have been uncovering
C: C. are uncovering
D: D. have uncovered
A: A. are being uncovered
B: B. have been uncovering
C: C. are uncovering
D: D. have uncovered
举一反三
- 4. We ________ on it for several hours but we have not yet reached any conclusion. A: A. work B: B. are working C: C. have been working D: D. have been worked
- We ______ on it for many hours, but we have not yet reached any conclusion. A: are being worked B: are working C: have been working D: have been worked
- 18. I’ll have to push the car to the side of the road because we ______ if we leave it here. a. will be fined b. would be fined c. will being fined d. will have been fined A: a. will be fined b. would be fined c. will being fined d. will have been fined B: b. would be fined c. will being fined d. will have been fined C: c. will being fined D: d. will have been fined
- We（）on it for many hours but we have not yet reached any concinsion. A: work B: have been worked C: have been working D: are working
- 【单选题】When ____you ____ supper? A. have; had B. do, have C. did, have D. will have A. have; had B. do; have C. did; have D. will have