The last time we had great fun was _____ we were visiting the Water Park.
| A．where | B．how | C．when | D．why |
We will work __________ those who have cheated in the exam and help them do right.
| A．off | B．on |
| C．at | D．with |
The hall began to fill up with people __________.
| A．by and by | B．sooner or later |
| C．little by little | D．all in all |
_________ is known to all that he can't answer the question __________ he found the money.
| A．As; how | B．That; why |
| C．What; where | D．It; when |
I would gladly pay __________ for the book, because it is quite a use- ful one.
| A．twice as much | B．twice so much |
| C．as much twice | D．so much twice |
__________ with the size of the whole earth, the highest mountain does not seem high at all.
| A．When compared | B．Compare |
| C．While comparing | D．Comparing |