Wind power is an ancient source of energy we may return in the near future.
| A．on which | B．by which | C．to which | D．from which |
(2012·上海) The club, __________ 25 years ago, is holding a party for past and present members.
| A．founded |
| B．founding |
| C．being founded |
| D．to be founded |
(2012·山东) After completing and signing it, please return the form to us in the envelope __________.
| A．providing |
| B．provided |
| C．having provided |
| D．provide |
"It’s sucha nice place," Mother said as she sat at the table __________ for customs.
| A．to be reserved |
| B．having reserved |
| C．reserving |
| D．reserved |
—Did you have any difficulty catching yesterday's lecture?
—No. The professor spoke very clearly to make his speech easy __________.
| A．understood |
| B．understand |
| C．understanding |
| D．to understand |
You should understand the traffic role by now. You've had it __________ often enough.
| A．explaining |
| B．to explain |
| C．explain |
| D．explained |