5. It was a great _____ for him to be pleasant to people he didn't like.
A. attempt
B. trouble
C. power
D. effort
[答案] D. effort.
[注释] effort (作可数名词用) (=vigorous attempt) 努力的尝试：Does it require a great effort of will to give up smoking? (戒烟需要坚强的毅力吗？)
