Only when the villagers were faced with water shortage___ how serious the problem of water pollution was．
| A．did they realize | B．will they realize | C．they did realize | D．were they realized |
They ______ the train until it disappeared in the distance.
| A．saw | B．watched | C．noticed | D．observed |
----- How long have you ______ the car?
----- For two months.
| A．bought | B．had | C．buy | D．borrowed |
So far nothing _____ Tom. I want to know the reason _______ he hasn’t written to me.
| A．heard from; why | B．has been heard from; why |
| C．was heard from; that | D．has heard from; that |
In the near future the computers ______ everywhere.
| A．can use | B．can be used | C．will use | D．are used |
We all write ______, even when there’s not much to say.
| A．now and then | B．by and by |
| C．step and step | D．more or less |