一艘快艇在平静的湖中起动并向湖边驶去，在这个过程中，水中的鱼、岸边飞翔的鸟、散步的人都可以听到马达声．若他们距艇的距离相似，那么他们察觉到快艇起动先后的是（ ）
A．鸟先于人
B．鱼先于鸟
C．人先于鱼
D．鸟先于鱼
声速的大小跟介质的种类有关，声音在水中的传播速度比在空气中快（水中的声速是1500m/s，空气中的声速是340m/s），所以在距离相同情况下，最先听到快艇启动的马达声的是鱼，这是因为声音在空气中比在水中传播速度慢．
故选B．
The 2010 Winter Olympic Games will take place in Vancouver and Whistler(惠斯勒) from February 12 to 28. As the world’s 小题1:_____ athletes will compete there, Canada is preparing for it well. It will be broadcasted(播出) in Canada’s two 小题2:_____languages——English and French. Billions of television viewers worldwide will 小题3:______ the opening ceremony of the 2010 Winter Olympic Games. Athletes from more than 80 小题4:______ will compete in 86 medal events over 17 days. Then the Paralympics(残奥会) will 小题5:_____ from March 12 to 21. Canada has 小题6:_____ millions of dollars preparing. Thousands of spectators will visit the country. Canada will be 小题7:_____ it all. The building of Olympic gyms began in 2005. Opening and closing ceremonies will be held indoors, at BC Place Stadium. It’ll 小题8:______55,000 seats. Some competitions, 小题9:______ ski, and bobsled, will take place in Whistler. It’s a ski village. During the Games, roads will be closed. More than 15,000 policemen will work to 小题10:______ the peace throughout the Games. The United States is the only country to host the Winter Games four times. Team USA hopes 2010 will be a golden year.
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