声音从声源发出,在空气中传播的过程中(设空气是均匀的) [ ]
A. 声波的波速不断减小
B. 声波的频率不断减小
C. 声波的响度不断减小
D. 以上都正确
答案:C
Mike started playing piano when he was 3 years old. [ ]
A. /
B. an
C. the
D. a
涂膜防水屋面子分部工程包含保温层、找平层、涂膜防水层、蓄水屋面。()