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
— How do you deal with the disagreement between the company and the customers?
— The key _____ the problem is to meet the demand _____ by the customers.
A. to solving; making B. to solve; making
C. to solving; made D. to solve; made
