______ life began on earth is one of the biggest puzzles that scientist found hard ______.
A. How; solving B. When; to be solved
C. How; to solve D. Which; to solve
Sir, you ________ take this seat. It’s just for the old.
A. oughtn’t to B. can’t C. won’t D. needn’t
Can you see that building ______ by trees? That’s ______ we study.
A. surrounded; which B. surrounding; where
C. to be surrounded; in which D. surrounded; where
I hate ______ when people call me by my nickname (绰号).
A. that B. one C. it D. 不填
_________ wants to enter for the match should reach the given standard.
A. Anyone B. The one C. Whoever D. Who
He said it was this classroom _______ he found his lost watch and _____ he would take good care of it from then on.
A. where; / B. when; what C. that; what D. where; that
________ many changes have _______, we should keep pace with the changes too.
A. Since; taken the place B. Because; taken place
C. Now that; taken place D. As; been taken place
______ the scene, he couldn’t help thinking of the description in a book ____ by a British novelist.
A. Seeing; written B. Seen; written
C. Being seen; writing D. Being seeing; written
I believe that those mountains ________ with trees in a few years’ time.
A. are covered B. will be covered C. are covering D. will cover