单选题 According to the passage the new telephone communication system, ______.
A. had been used within limited scope before 1977.
B. was first put into actual use in 1977.
C. had been repeatedly experimented on before 1977.
D. was put on experiment in 1977.

【正确答案】 D

【答案解析】推理题。本题问这种新的电话通信系统______。根据文章第一段第六句“Called lightwave communication，the new system was used successfully in an experiment in Chicago in 1977.”可知选D。