The policeman was ________ abusing his power when performing his duty, but it hasn’t been ______ yet. 

People have planted a lot of trees and grass in order to ____ wind and sand in the desert．

We can’t            against other countries in trade if we don’t develop our national economy(经济).

All the students ______ to inform their parents _______ the mid-term exam results.

We ____ that the magazines you have borrowed be returned to the school library before the end of this month．