They can swim (改为一般疑问句）

正确答案是：
They can swim (改为一般疑问句）
- Can they swim?
注释：只要把情态动词“can”移到句首即可.
He often helps his mother do the housework(改为同义句）
He often helps his mother with the housework.
注释：help sb.do sth.= help sb.with sth.