问题补充：
What great trouble the boy his father to give up smoking!
A. had to persuade
B. had persuaded
C. had persuading
D. had persuade
答案：
A. had to persuade
B. had persuaded
(答案→)C. had persuading
D. had persuade
解析：考查固定句型。做此题时应注意将题干还原成陈述句结构：The boy had great trouble (in)persuading his father to give up smoking。have trouble/problems/a hard time (in) doing sth表示做某事非常费力，句中的in可以省略。句意：那男孩说服他父亲戒烟费了多大劲啊！ 故C正确。
