Question

It was after dark when the two children were both on the safety crossing by a lorry

A knocked down B knocked out C yun out D runacross 解释一下
both后面有横线 C run out D run across

Answer 1

1.前面有个were，说明此句后面只能接过去分词构成被动语态.（ABCD都对）
2.补充的内容是 两个孩子被汽车.....怎么了
3.再看这几个词组的意思：（因为都是过去分词需去掉后缀）
A.knock down 击倒；撞倒
B.knocked out 敲空；击倒；打破
C.run out耗尽；跑出；到期；伸向
Drun across偶然遇到；跑着穿过

很显然BCD放上去都不合语意，所以选A knock down 撞倒