Can you swim?就可以了 回答的形式分两种：肯定形式 Yes, I can. 否定形式 No, I can't.
应该是Can't you swim?回答有两种：Yes ,I can.（不，我会游泳）No,I can't.(是的，我不会游泳）
用否定问Can't you swim?Yes ,I can.No,I can't.
