—Could you tell me whom the radio _____ by?

—Sorry, I have no idea. [ ]

A. invents

B. invented

C. is invented

D. was invented

20世纪50年代初，美国干涉中国内政最严重事件是 [ ]

A．侵略朝鲜

B．派第七舰队到台湾海峡

C．将战火烧到鸭绿江边

D．敌视中国