Complete the sentenced with the given words in their proper forms（用括号中所给单词的适当形式完成下列句子）

【1】The environment will be ________ polluted if people don't take any action.（serious）

【2】Tom practised ________ the piano every night.（play）

【3】This new policy aims to ________ the refugees（难民）.（protective）

【4】Mary has invited us ________ her performance.（watch）

【5】Countless buildings were ________ during the WenChuan earthquake.（destruction）

【6】There are ________ methods we people can take to save our earth.（variety）

【7】My sister often ________ prices when she goes shopping.（comparative）

【8】The road is now less ________ for walkers because it was widened last year.（danger）