when he jumped from the tree ,he lost his balance and broke his right arm .
问题描述：
when he jumped from the tree ,he lost his balance and broke his right arm .
为什么不用was jumping?还是都行
答
不可以, jumped 表示这个动作完成了,结果是右手断了,be doing表示过去进行时,was jumping不通,jump这个动作不可能一直进行（那得多高的树呀）,而且后面lost是过去时态,也说明了用jumped,表示这个动作已经完成,故用完成时,而不能用过去进行时