问题补充：
When Peter speaks in public, he always has trouble _ the right things to say.
A. thinking of
B. to think of
C. thought of
D. think of
答案：
(答案→)A. thinking of
B. to think of
C. thought of
D. think of
解析：本题考查固定搭配，have trouble in doing sth.做…有困难，in可以省略，句意：当彼得在公共场所讲话时，他总是找不到适当的话说。所以答案为A。
