用下列方框内的词或短语的适当形式完成句子，每项只能用一次。

1．The boy is so clever that he can work out this problem by           .

2．My task is           a good idea as soon as possible.

3．           other people is an impolite behavior.

4．—How long have you been           ?

—Four nearly 40 years.

5．The           desk was bought by my father 7 years ago.