We need to get to the root of the problem______ we can solve it.
| A．while | B．after | C．before | D．as |
.
________ on the subject for half an hour, Liu Ying suddenly stopped.
| A．To be worked | B．To work |
| C．Having worked | D．Having been worked |
.
She offered me practical ________ with my research, for which I would appreciate for my whole life.
| A．conduct | B．certificate | C．admiration | D．assistance |
.
“ Look at him! He behaved ________ nothing had happened”, said Mary.
| A．as if | B．even if | C．if | D．unless |
.
They were singing and dancing to ________ their high spirits though it was very cold.
| A．keep up | B．build up | C．bring up | D．pick up |
.
The weather is so ________ this year that we can hardly stand so many cold days!
| A．wonderful | B．awful | C．absurd | D．accessible |