问题
选择题
We tried ______ to persuade him to stay home, but at last, he went to the construction site despite his bad illness.
A．in case
B．in vain
C．in fact
D．in addition
答案
答案：B
考查介词短语。我们尽力地说服他呆在家里，但是徒劳的。故用in vain.