______ it have been the failure to pick up directions from the ground control that caused the air crash?
| A．Must | B．Could | C．Would | D．Should |
32. If the economic situation goes on like this, t
here’s a danger______ many factories may have to close down.
| A．as | B．when | C．whether | D．That |
31. —You should make it a rule to do more exercise
in your spare time.
— I think your suggestion really deserves__________.
| A．considering | B．to consider | C．being considered | D．Considered |
30. —What should we do since we can’t make a compromise after lengthy talks.
— ____ you apologize and take back what you’ve said _____ it is all over between us.
| A．Not only; but also | B．Either; or | C．Neither; nor | D．Whether; or |
29. Tired of work through the year, she desired to _____ and make an independent life for
herself.
| A．drop off | B．drop in | C．drop out | D．drop behind |
28. The book was written _____ careful observations and detailed studies.
| A．on the ground of | B．on behalf of | C．on average | D．on the basis of |