行过路过,不要错过The policeman was wounded ___,but he caught the rob

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

B
his knee他的膝盖
cacth by the arm/leg 是固定用语