[求助]问个关于被动语态的题目，谢谢大家帮忙了

Although early soap operas were first aired on evening radio in the 1920's,they had moved to the day time hours of the 1930's when the evening schedule became crowded with comedians and variety shows.

A.were first aired on evening radio in the 1920's,they had moved to the day time hours of the 1930's

B.were first aired on evening radio in the 1920's,they were moved to the day time hours of the 1930's

C.were first aired on evening radio in the 1920's,moving to the day time hours of the 1930's

D.were first aired on evening radio in the 1920's,they moved to the day time hours of the 1930's

E.aired on evening radio first in the 1920's,they were moved to the 1930's in the daytime hours

                                                                                                 Answer:B

拜托各位能不能帮我详细解释一下哦，书上的解释太简单了。谢谢！