题目内容：
Questionsarebasedonthefollowingpassage:
Firecanhelppeopleinmanyways．Butitcanbeverydangerous．Firecanheatwater,warmhouses,givelightandcook．Butfirecanbumthings,too．Itcanburntrees,houses,animalsorpeople．Sometimesbigfirescanburnforests．
Nobodyknowsforsurehowpeoplebegantousefire．Buttherearemanyinterestingstoriesaboutthefirsttimeamanorawomanstartedafire．OnestoryfromAustraliatellsaboutamanvery,verylongtimeago．Hewentuptothesunbyarope(绳子)andbroughtfiredown．
Todaypeopleknowhowtomakeafirewithmatches(火柴)．Childrensometimesliketoplaywiththem．Butmatchescanbeverydangerous．Onematchcanburnapieceofpaperandthenitmightburnahouse．Asmallfirecanbecomeabigfireveryfast．Firekillsmanypeopleeveryyear．Soyoumustbecarefulwithmatches．Youshouldalsolearntoputoutfires．Firesneedoxygen(氧气)．
Withoutoxygentheywilldie．Coverafirewithwater,sand,orsometimeswithyourcoat．Thiskeepstheairawayfromafireandkillsit．Becarefulwithfire,anditwillhelpyou．Becarelesswithfire,anditwillburnyou．
Howdidpeoplebegintousefire? A．Noteverybodyknowshowpeoplebegantousefire
B．Nobodyknowshowtomakeafire
C．ItisanAustralianwhostartedafire
D．Wearenotsurehowpeoplebegantousefire
参考答案：
答案解析：