Computers can do nothing．But once ______what to do, they show extraordinary power to do a great deal．
| A．to program | B．being programmed |
| C．programmed | D．having programmed |
_______ twice a year, whether it is a car or a bus or a
truck, is the rule that every driver must obey in this city．
| A．Being examined | B．Examining |
| C．Examined | D．Having been examined |
What a pity! ________joined in the party, I would have met my old friend．
| A．lf I have | B．Had I | C．I had | D．Have I |
Today's homework was easy _______so I finished it quickly and went out to play．
| A．to be done | B．done | C．d oing |
D．to do |
Don't you think _______of great importance that we should keep fit by taking exercise regularly?
| A．this | B．that | C．which | D．it |