题目内容：

The old man with his son_______the street carefully when the traffic light was red.
A.were crossing B.crossed C.across

优质解答

The old man with his son （A.were crossing） the street carefully when the traffic light was red.当红灯亮时,那位老人正和他的儿子一起小心地过马路.时间状语为when引导的过去时,主句为过去进行时态,表示过去...

追问：

答案是C

追答：

这个所谓的答案肯定是错的了。across是个介词，而这里应该是填个动词作为句子的谓语。选择C项太离谱了。