问题
选择题
Mr. Smith didn’t understand _____ made his son so upset that evening.
A．what was it
B．why it was this
C．how that was
D．what it was that
答案
答案：D
考查强调句型it be +被强调部分+that…;又因为句中缺少understand的宾语从句的主语所以用what，选D. 史密斯先生不知道那晚到底是什么事情使得他的儿子如此伤心。