I could have helped the old man ______ yesterday morning.
| A．did I come | B．if I came | C．had I come | D．if I should come |
Nobody is allowed to go through the between China and Russia without a passport.
| A．booth | B．bush |
| C．border | D．buffet |
Barack Obama’s first speech as president left a strong impression his audience.
| A．on | B．in | C．at | D．by |
It has been proved eating vegetables in childhood helps to protect you against serious illnesses in later life.
| A．if | B．because |
| C．when | D．that |
we’ll go travelling abroad next year depends on how much we will have earned.
| A．If | B．That |
| C．Whether | D．When |
Many animals use their colours to themselves from .
| A．prevent; eating | B．protect; eating |
| C．protect; being eaten | D．keep; eating |