【单选题】
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
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根据网考网移动考试中心的统计,该试题:
4%的考友选择了A选项
17%的考友选择了B选项
3%的考友选择了C选项
76%的考友选择了D选项