Section_ⅠIntroduction & Reading - Pre­reading

　　[原文呈现]

　　What Is a Tornado①？

　　A tornado is a rotating② column③ of air from a thunderstorm④ to the ground. The most violent⑤ have winds of more than 400 kilometres per⑥ hour. Almost all of them occur⑦ in the US, in the area from Texas in the southeast to South Dakota in the north.

　　Tornadoes can pick up⑧ cars, trains and even houses and put them down in the next street - or even in the next town. They can take the fur⑨ off⑩ the back of a cat and the feathers⑪ off a chicken. They can destroy houses, but leave the furniture⑫ inside exactly where it was⑬.

　　On average⑭， there are 800 tornadoes in the US each year, causing⑮ about 80 deaths and 1,500 injuries⑯. The worst tornado of all time⑰ occurred in 1925, affecting three US states⑱： Missouri, Illinois and Indiana. By the time it ended, more than 700 people had been killed and 2,700 had been injured.

　　[读文清障]

　　①tornado/tɔː'neIdəʊ/n.龙卷风

　　②rotating/rəʊ'teItIŋ/adj.旋转的；循环的

　　③column/'kɒləm/n.柱状物；柱状体

　　④thunderstorm/'θʌndəˌstɔːm/n.雷暴

　　⑤violent/'vaIələnt/adj.猛烈的；激烈的；强烈的

　　⑥per prep.每

　　⑦occur/ə'kɜː/vi.发生

　　occur不用于被动语态和进行时态。

　　⑧pick up卷起；掀起

　　⑨fur/fɜː/n.(动物的)毛皮　⑩take off 去掉

　　⑪feather/'feðə/n.羽毛　⑫furniture/'fɜːnItʃə/n.家具

　　⑬where it was是where引导的地点状语从句。

　　⑭on average 平均起来　⑮cause/kɔːz/vt.引起；导致

　　⑯causing about 80 deaths and 1,500 injuries是现在分词短语作结果状语。

　　⑰of all time有史以来，历史上(常与最高级连用)

⑱现在分词短语affecting three US states作状语，表结果。