Only in 1996 the determination and patience of the scientists with a breakthrough at last .
| A．were ; paid off | B．did; pay back | C．did ; pay off | D．did ; pay for |
35. Although this___________sound like a simple task, great care is needed.
| A．must | B．may | C．shall | D．Should |
34、It must have rained last night, ___________?
| A．mustn’t it | B．can’t it | C．hasn’t it | D．didn’t it |
33. It is surprising that he_______have been such foolish, he never made such a mistake.
| A．must | B．could | C．should | D．Might |
32. －Kate, what is wrong with your pen again? There is not enough time.
－The ink_____come out.
| A．doesn’t | B．won’t | C．hasn’t | D．can’t |
31. They arrived at a farmhouse, in front of ___________sat a small boy.
| A．whom | B．where | C．which | D．That |