问题描述: by表示被动? 1个回答 分类:综合 2014-11-24 问题解答: 我来补答 He was knocked down by a car when crossing the street.本句为被动句,但是by在语法上并不表被动 be knocked down才表被动,而by只是修饰作用. 展开全文阅读