He is good at maths and it won’t be long ____ he works out the problem.
| A．since | B．until | C．before | D．when |
_______I came to the music hall ,it was a new and grand one .
| A．Firstly | B．For the first time | C．The first time | D．First time |
_____ of the students who took part in the military training is 750.
| A．A number | B．A lot | C．Dozens | D．The number |
What way are you thinking of _____ rid of the flies?
| A．to get | B．getting | C．being got | D．to be getting |
It is difficult to imagine his _____ the decision without any consideration.
| A．accept | B．accepting | C．to accept | D．accepted |
When the space ship was ____, I could really feel the high gravity.
| A．lifting off | B．landing | C．sending away | D．giving a lift |