Computers ____ in offices and homes since 1970s.
| A．have been used | B．had been used | C．was used | D．has been used |
There are two small rooms in the house, _____ serves as a kitchen
| A．the smaller of which | B．the smallest of which |
| C．the smaller of them | D．the smaller one |
This is the very knife _____ I used to cut apples yesterday.
| A．that | B．by which | C．which | D．with which |
---- Is it high time that we _____ on the school building?
---- Yes, it _____.
| A．do some repairs; is | B．do some repair; is |
| C．did some repairs; is | D．did some repair; was |
The cost of sales makes up a large part of the prices that _____.
| A．are paid for all products |
| B．all products are paid |
| C．for which all products are paid |
| D．for all products paid |
The captain stood by the window, _____ he could see the top of the tower.
| A．where | B．from which |
| C．from where | D．which |