A是对的.
我觉得你的题目应该是The policeman was wounded by___, but he caught the robber by ___.
这样就对了!
这是一个很常用的固定用法,通常用被动:
be wounded by the knee
be caught by the arm
指某某部位被怎么样了
例如:i was kicked by the leg by that boy yesterday.
注意:第一个by是上面的用法,第二个by就是被……人的意思了
用主动语态也可以:
he caught him by the arm
he kicked me by the leg