magazine Nature.

　　The whales travel in groups，and communicate with each other through sonic calls that some scientists refer to as singing.The sounds of the boat engines may be creating too much background noise for the whales to be able to hear each other.

　　The researchers listened to recordings of whale calls made between 15 and 25 years ago，before whale watching became popular.These were compared to more recent recordings.

　　They found that the animals have started to sing for longer than they used to, like a person shouting to a friend across a noisy room.

　　It is believed that the whales are trying to communicate hunting or breeding information.Scientists said that，if this is prevented，the future of the world's whale population could be in danger.

　　"Animals become slow in mind and repeat themselves in noisy areas，"said Volker Deecke，a Canadian biologist."They have to say things twice or three times in order to be understood."

　　The killer whales studied were living off the coast of northwestern America.The number of killer whales in this area has been falling for several years，but scientists are not sure why.

　　【语篇解读】　本文首先介绍了观鲸船所产生的噪音对虎鲸的交流造成了困难，然后又介绍了观鲸旅游的盛行和虎鲸的交流方式。

　　1．The passage mainly tells us ．

　　A．the problems of whale watching

　　B．how killer whales communicate with each other

　　C．the reduced population of killer whales caused by whale watching

　　D．hearing problems of the killer whales caused by whale watching

　　D　[主旨大意题。概括文章第一段可得出答案。观鲸船的噪音给虎鲸的信息交流造成了困难。A项所涉范围过大；B项仅仅是文章的细节；C项与原文信息不符，因为文章最后说虎鲸数量下降的原因不明。]

2．Now in a noisy background, the killer whales have to ．