16. __ kinds of dinosaurs were dying out all through the Age of Reptiles is true.
A. Some
B. Some were
C. When some
D. That some
17._________to blame for the many troubles you have encountered.
A. It is notIwhoam
B. It is notIthatis
C. It is not me who am
D. It is not me that is
18. He noticed the helicopter hovering over the field. Then to his astonishment, he saw a rope ladder_________out and three men climbing down it.
A. throwing
B. being thrown
C. having thrown
D. having been thrown
19. The physicist has made a discovery,____of great importance to the progress of sci-ence and technology.
A. I think which is
B. that I think is
C. which I think is
D. which I think it is
20. As it turned out to be a small house party, we so formally.
A. need not have dressed up
B. must not have dressed up
C. did not need to dress up
D. must not dress up