—Have you known Dr. Jackson for a long time?—Yes, since she________ the Chinese Society.

In order to find the missing boy, the young couple            all they can over the past twenty-four hours. 

Where were you at lunch time? I   a seat for you in the dining hall.

The Chinese government has made great efforts to ______ the gap between the rich and the poor, but has not achieved obvious results.

In the past decades, sea ice ______ in the Arctic as a result of global warming.