Action must be taken to prevent that factory from ______ heavy smoke into the air.
| A．giving off | B．putting away | C．escaping from | D．dealing with |
A small car is big for family of three_______ you need more space for luggage.
| A．once | B．because | C．if | D．unless |
The reason______ she failed to go to the party puzzled all of the people present.
| A．what | B．why | C．as | D．which |
In the U.S, ______a tip is thought to be polite when paying the bill.
| A．leave | B．having left | C．leaving | D．being left |
He is the only one of those clerks ________ to the important conference.
| A．who was inviting | B．who were invited |
| C．who has been invited | D．who have been invited. |
When I turned to Tony for help, I found that the more he tried to explain, ___________.
| A．the more I became confused. | B．the more confused became I |
| C．the more confused I became | D．I became more confused. |