the old man fell down and hurt his knees by a_____

问题描述:

the old man fell down and hurt his knees by a_____

accident
by accident是一次意外的意思。
整句话就是:这位老人意外(不小心)摔倒了,弄伤了他的膝盖
希望能帮助你

accident
老人意外摔倒伤到了膝盖。

答案:accident
不明白的再问哟,请及时采纳,多谢!

by accident 偶然,无意