超声波是人耳听不到的声波,其频率大于多少赫兹?()
A.1 000 Hz
B.2 000 Hz
C.20 kHz
D.10 kHz
参考答案:C
—I need to get changed. —________! We’ll be late for the party.
A.Oh, come on
B.Go ahead
C.Take it easy
D.It’s a pity
—What language can they speak?
—_______. [ ]
A. Japan
B. Japanese
C. China
D. a Chinese