One night ,when he was on duty in the bank,a robber broke into it and___him ___a gun.
问题描述：
One night ,when he was on duty in the bank,a robber broke into it and___him ___a gun.
A.frightened;by B.threatened;with C.feared;at D.surprised;through
请说明理由
答
threaten sb with sth 用什么东西恐吓某人