materials they can find on poor clay\s\up1(37(37) soil\s\up1(38(38). These homes, seldom made of bricks\s\up1(39(39)， can easily fall down in earthquakes or slip\s\up1(40(40) and slide\s\up1(41(41) downhill in landslides, especially in mountainous\s\up1(42(42) areas. (4)________ This has mainly been caused by the huge amounts of carbon dioxide produced by factories and vehicles, and the destruction\s\up1(43(43) of the world's forests. As a result, a hotter ocean causes more powerful winds. Atlantic hurricanes - their howling\s\up1(44(44) winds with speeds of over 300 kilometres an hour - are 40% stronger now than they were 30 years ago.

　　D

　　Volcanoes and earthquakes are even more dangerous than in the past as around half the world's population now lives in cities\s\up1(45(45).There are more than 300 active volcanoes, about fifty of which erupt\s\up1(46(46) each year, and more than 500 million people now live within the range of\s\up1(47(47) a volcanic eruption. Because these natural disasters occur at random\s\up1(48(48) times, it is difficult to warn people in advance\s\up1(49(49). In May 2006, thousands of Indonesians living near Mt Merapi (which means mountain of fire) had to flee\s\up1(50(50) as they thought it was about to erupt. An even greater number of people live at risk\s\up1(51(51)， to some degree\s\up1(52(52)， from earthquakes which have claimed\s\up1(53(53) more than 1.6 million lives in the last hundred years.

　　E

　　Most disaster experts believe there is the potential\s\up1(54(54) that\s\up1(55(55) things could get a lot worse. Professor Hou Ming, of Beijing University studies volcanoes and he warns that the world has not seen the worst nature can do. The worst eruption in human history was probably Mt Tambora in 1815, in Indonesia. Dust\s\up1(56(56) from the volcano rolled\s\up1(57(57) across the Earth's skies and pretty\s\up1(58(58) much cancelled the following summer in Europe and America. (5)________ "It reduced temperatures by maybe 6℃ in some places and the whole planet was sent into winter for years. And there are about two of these events every 100,000 years ..."

　　⑰threat n．[C]威胁；恐吓

　　⑱wipe out 彻底毁灭，去除

　　⑲rough/rʌf/adj.艰难的

　　⑳have a rough time过得很艰难，过着艰难的生活

　　\s\up1(21(21)suffer vt.遭受，承受

　　\s\up1(22(22)quake/kweIk/n.地震

　　suffering several killer quakes 是现在分词短语作伴随状语。

\s\up1(23(23)recover from 从......中恢复