声音在空气（15℃）中传播的速度为______米/秒，若在峡谷中呼喊，从发声到听到回声历时3秒，那么峭壁离人的距离为______米．
（1）声音在空气（15℃）中传播的速度为340m/s；
（2）声音从发出到峭壁的时间t=
×3s=1.5s，1 2
∵v=s t
∴峭壁离人的距离：
s=vt=340m/s×1.5s=510m．
故答案为：340；510．
Passage Three
What mistaken view do most people hold about Arabic
A．Colloquial Arabic is the everyday spoken language, which varies from country to country.
B．Arabic is just one language that all Arabs understand, speak and write.
C．Classical Arabic and Modem Arabic are two different kinds of written Arabic.
D．Pan-Arabic provides a means of communication between educated people of different Arab nationalities.