knowtaewaysyoucanuseandshowthemtoeveryoneinthefamily．suchasstairwaysandfireescapes，batnotlifts．可以推出答案为D。
　　44．A[解析]由Keepyourheadlowatthewindowtobesureyougetfreshairratherthansmokethatmayleaked(渗)intotheroom．可推出A正确。
　　45．B [解析]根据短文的主要内容，比较四个选项，B为最佳。
　　Ⅳ．单词拼写
　　46．deservetoberespected
　　47．(that)Ihadleftmywallet／purseathome
　　48.tells／toldusnottobenervous
　　49.Iamnotsurewhether/if
　　50.Nomatterhowhard/difficultitis
　　V．书面表达
　　One possible version:
　　People cut down too many trees and leave rubbish everywhere. Factories let out their waste without doing anything to it. This has caused some serious problems. For example, the land is sandy; the river is dirty; the air is less clean; even the temperature of the earth is rising, and she is shouting for help. What shall we do to save her? My suggestion is that we should plant more trees, put the rubbish into dustbins and stop factories pouring waste into the air or rivers. We have only one earth, we should do everything to protect it, or we will regret.