第2题: [单项选择]According to the passage the new telephone communication system ______. A. has been put into actual use B. was put into actual use in 1977 C. was put on experiment in 1977 D. had been repeatedly experimented on before 1977 参考答案:C 答案解析:[分析] 第三段第一句……,the new system was used successfully in an experiment in Chicago in 1977.答案选C。