The chairman’s speech the radio when I turned it on.A. was broadcast onB. was being broad

问题补充：

The chairman’s speech the radio when I turned it on.

A. was broadcast on

B. was being broadcast on

C. was broadcasting in

D. broadcast over

答案：

A. was broadcast on

(答案→)B. was being broadcast on

C. was broadcasting in

D. broadcast over

解析：考查时态以及介词的用法。从when I turned it on可知，前句应该用同进行时有关的时态；broadcast与speech之间存在被动关系，“通过收音机”可以用over/on the radio。“通过电视”则说：on TV（无冠词）,“通过报纸”through newspapers。