The engineers made two big plans for the dam, ____ was never put in force.
| A．one of them | B．which | C．one of which | D．every one of which |
Several weeks had gone by _______ we realized the painting was missing.
| A．as | B．since |
C．before | D．when |
Although _______ of danger, tourists can't help taking photos near the cliff.
| A．having warned | B．warned |
| C．warning | D．to be warned |
Many websites have been _______ to help people study foreign languages.
| A．put off | B．put up |
C．put away | D．put on |
---Can I join the club, Dad?
---You can when you ______ a bit old.
| A．get | B．will get |
| C．are getting | D．will have got |
The hotel wanted to charge 50$ for the room service, but we couldn’t ______ to live in such an expensive hotel.
| A．spend | B．afford |
| C．charge | D．pay |