1. 用方框内所给单词或短语的适当形式完成下列句子（有一项多余）

true    deal   refuse    work    dress    be able to

1. （1） He is old enough himself.
3. （2） The doctor warned Mr Li not so hard every day.
5. （3） I don't know how with the difficult problem.
7. （4） When Dan was seven years old, he play the piano very well.
9. （5） The best thing would be to tell him the .