When Peter speaks in public he always has difficulty the right things to say.A. thinking

问题补充：

When Peter speaks in public, he always has difficulty the right things to say.

A. thinking of

B. to think of

C. thought of

D. think of

答案：

A. thinking of

B. to think of

C. thought of

D. think of

解析：考查固定词组。固定词组have some difficulty (in) doing sth做某事有困难。句意：当Peter当众发言的时候，他总是很难想起要说的事情。故A正确。