A car broke down and that was ____ caused the traffic jam.
问题描述：
A car broke down and that was ____ caused the traffic jam.
A.howB.why C.whichD.what
为什么选D,不选B
答
was缺少表语,而 caused 缺少主语,在下面4个选项中,只有what 可以作为两种成分,what 也可译为 that that ,第一个that 为was的表语,第二个that为caused 的主语