1£®Scientists have tried many ways __to_solve__(solve) this problem and in China, a mass campaign has been started __to_help__(help) solve it.

2£®The storms sometimes continue all day and traffic moves very slowly because the thick dust makes it difficult __to_see__(see)£®

3£®Weather experts advise people not __to_go__(go) out.

4£®It's difficult __to_breathe__(breathe) and the dust makes me ill.So if you want __to_go__(go) out, you'd better wear a mask.

5£®__To_prevent__(prevent) it coming nearer, the government is planting trees.