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
网友回答
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。