_______man must fear when travelling in space is radiation from the sun.
| A． Which | B． How | C． What | D． That |
We liked the oil painting better____________ we looked at it.
| A．as | B．while | C．the | D．the more |
— Show me your permit, please.
—Oh, it's not in my pocket. It
| A．might fall out | B．could fall out |
| C．should have fallen out | D．must have fallen out |
We must keep our room clean. Dirt and disease go _____ you know.
| A．from time to time | B．hand in hand |
| C．step by step | D．one after another |
I tried hard to get some information about the new technology out of his mouth, but he remained____________.
| A．quiet | B．secret | C．silent | D．calm |
--Could I use your bike, Jack?
--Of course, you____________.
| A．can | B．may | C．could | D．might |