just spend your time___ gains and losses, maybeyou’ll get nothing in the end．

I have been told that our visit to Mount Tai will be cancelled because a very important foreign delegation (代表团) will be there.—-Oh, no！______.

Attention, please. The plane has to be put ______ because of the heavy fog.—Oh, bad luck! We have to wait now.

_______ is easy for many students to _______ to school.

There _______ a pen and two books on the desk.