_________ in the fields on a March afternoon，he could feel the warmth of spring．
| A．To walk | B．Walking |
| C．Walked | D．Having walked |
I _____ through the hard time but for my teacher’s generous and timely help．
| A．couldn’t have gone | B．could go |
| C．mustn’t have gone | D．hadn’t gone |
The class teacher was anxious to hear one of his top students _____ because of family move．
| A．will leave | B．is leaving |
| C．was leaving | D．has left |
With the exam ______ in ten minutes, they were asked to hand in their mobile phones．
| A．taken place | B．taking place |
| C．having taken place | D．to take place |
More than one doctor _____ involved in the rescue that took place after the earthquake．
| A．was | B．is | C．were | D．are |
Some hard working students always keep a torch in their dormitories _____ there is a power failure．
| A．if | B．unless |
| C．so that | D．in case |