问题
单项选择题
Radio communication（）for many years and helps to save tens of thousands of lives.
A.has been used
B.have been used
C.has used
D.have used
答案
参考答案：A
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Radio communication（）for many years and helps to save tens of thousands of lives.
A.has been used
B.have been used
C.has used
D.have used
参考答案：A