Ex1:Choose the best word or phrase (A, B or C ) to complete each sentence below 
1. Don't drink that water. It's ________           A.damaged            B.dumped        C.contaminated
2.Several tropical storms ___________ our country recently. 
  A.struck          B.have struck    C.are striking     
3.The victims on the roofs of the houses ___________ with food and water by the rescue team.
A.provided     B.will be provide    C.were provided     
4.If we _______ soon, the pollution will get much worse.     A.don't act     B.didn't act           C.will not act             
5.I learnt from the news on TV that the earthquake ___________ hundreds of houses.
A.destroys               B.were destroyed         C.had destroyed