Earth is believed ______ by an object the size of Mars at some point in the distant past
before its surface cooled．
| A．to be hit | B．to have hit | C．to have been hit | D．to hit |
Even though I’d hurt my leg, I______swim back to the river bank.
| A．could | B．might | C．had to | D．was able to |
—Do you think he will do me a favor?
— As far as I know, he is the last one to help others. He______be prepared to give you a hand, though.
| A．might | B．must | C．can | D．should |
Hurry up,Tom.It’s high time we______ to the theater.
| A．will | B．shall | C．are going to | D．went |
What ______ had Bob walked farther, as far as the river bank?
| A．would happen | B．could happen | C．would have happened | D．needn’t have happened |
— What happened to the young trees we planted last week?
—The trees______well, but I didn’t water them.
| A．might grow | B．needn’t have grown | C．would grow | D．would have grown |