单项选择题
A.389m/s,439m/s,467m/s B.389m/s,420m/s,477m/s C.389m/s,439m/s,477m/s D.380m/s,439m/s,477m/s
A.2.0 B.-1.5 C.-1.0 D.3.0
A.1000Hz B.1050Hz C.1063Hz D.1062Hz