There was a look on his face. He found what the expert said too difficult to understand.A

问题补充：

There was a look on his face. He found what the expert said too difficult to understand.

A. puzzle

B. puzzling

C. puzzled

D. to puzzle

答案：

A. puzzle

B. puzzling

(答案→)C. puzzled

D. to puzzle

解析：puzzled形容词可以用来形容人，也可形容人的声音或表情。“他脸上带着困惑的表情，他发现专家所说的内容太难理解。”