We are using of law great effect.A. the arms; inB. the weapons; ofC. the weapon; withD.

问题补充：

We are using of law great effect.

A. the arms; in

B. the weapons; of

C. the weapon; with

D. the arm; by

答案：

A. the arms; in

B. the weapons; of

(答案→)C. the weapon; with

D. the arm; by

解析：考查名词及介词。the weapons of law=法律武器。weapons泛指一切武器，包括具体和抽象的arms一般指武装。with effect 固定搭配，意思是具有成效。故选C。