With the help of high technology, more and more new substances ______ in the past years.
A. discovered B. have discovered
C. had been discovered D. have been discovered
--- Guess what! I have got A for my term paper.
--- Great! You ______ read widely and put a lot of work into it.
A. must B. should C. must have D. should have
--- Did you tidy your room?
--- No, I was going to tidy my room but I ______ visitors.
A. had B. have C. have had D. will have
Alan is a careful driver, but he drives ______ of my friends.
A. more carefully B. the most carefully C. less carefully D. the least carefully
The mayor has offered a reward of $ 5000 to ______ who can capture the tiger alive or dead.
A. both B. others C. anyone D. another
Leaves are found on all kinds of trees, but they differ greatly ________ size and shape.
A. on B. from C. by D. in
