The children are busy doing piles of homework, for they _______ their end-of-term exam soon.

--- You've left the light on.　 --- Oh , so I have.  _____and turn it off.

—Have you heard about the recent election?—Sure, it _______ the only thing on the news over the last three days.

I _____ Wang Tao in the street yesterday. We _____ each other since he went to Beijing.

The old man __________ in Tibet for two years as a volunteer teacher；it is an experience he  often mentions.