问题
选择题
It took a great deal of courage to admit that all their efforts had been ________.
A．in danger
B．in vain
C．in return
D．in turn
答案
答案：B
B [in danger处于危险中；in turn反过来；in return作为报答；in vain白费力气，徒劳无益。句意：他们需要有很大的勇气承认自己的一切努力全是徒劳的。]