Yesterday, when I went to his office, he ______ online for some information. I think it will be an interesting lecture.
| A．searched | B．was searching | C．would search | D．has searched |
Experiments of this kind __________ in both the U. S. and Europe well before the Second World War.
| A．have conducted |
| B．have been conducted |
| C．had conducted |
| D．had been conducted |
It's no use __________ without taking action.
| A．complain |
| B．complaining |
| C．being complained |
| D．to be complained |
Even the best writers sometimes find themselves __________ for words.
| A．lose |
| B．lost |
| C．to lose |
| D．having lost |
I am afraid he's more of a talker than a doer, which is __________ he never finishes anything.
| A．that |
| B．when |
| C．where |
| D．why |
Claire had her luggage __________ an hour before her plane left.
| A．check |
| B．checking |
| C．to check |
| D．checked |