The secretary worked late into the night, ________ a long speech for the president.

We watch the children _______ into the water from the _____ board.

Of the three statements he has suggested __ the heating problem, I think the last one is the best. 

If I         long enough to have a job, I would choose to be a doctor,      those AIDS patients．

________about her son’s future, the mother has been sleeping very badly these months.