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【单选题】
中国古代守城时，为了防止敌人挖掘地道入城，城中设有“___”，即用陶盆覆于井口，命听觉灵敏的士兵轮流值班，以耳贴翁，倾听有无异样声音。
A.
地听
B.
天视
参考答案：
参考解析：
刷刷题刷刷变学霸
举一反三
【单选题】Every year television stations receive hundreds of complaints about the loudness of advertisements. However, federal rules forbid the practice of making ads louder than the programming. In addition, t...
A.
TV stations always operate at the highest sound levels
B.
their sound levels are kept around peak levels
C.
their sound levels are kept in the middle frequency ranges
D.
unlike regular programs their intensity of sound varies over a wide range