适当形式填空:While ___(climb) up the hill,the old man often sat down and had a rest.
问题描述：
适当形式填空:While ___(climb) up the hill,the old man often sat down and had a rest.
答
While 【climbing】(climb) up the hill,the old man often sat down and had a rest.
答
climbing=While he was climbing up the hill,
在爬山的时候,那位老人经常坐下来休息一下.