按要求填空,每空一词

按要求填空,每空一词
1,He looks sad ；let’s cheer him up（改为同义句）
He looks sad ；let's（ ）him （）
2,He could swim when he was five（改为同义句）
He （ ）（）（ ）swim when he was five
3,He told me about his problems（改为否定句）
He （）（）me about his problems
4,I don't know how I can help him （改为同义句）
I don't know（）（ ）（）
5,He takes after his mother （改为同义句）
He （ ）（ ）his mother