题目内容：
Questionsarebasedonthefollowingpassage:
Anotherthinganastronauthastolearnaboutiseatinginspace．Foodisweightless,justasmenare．
Foodforspacehastobepackedinspecialways．Someofitgoesintotubesthatamancansqueezeintohismouth．Bite-sizedcookiesarepackedinplastic．
Thereisagoodreasonforcoveringeachbite,Theplastickeepspiecesoffoodfromtravelinginthespaceship．Ontheearthverysmallpiecesoffoodwouldsimplyfalltothefloor．Butgravitydoesn'tpullthemtothefloorwhentheyareoutoftheplasticinaspaceship．Theymovehereandthereandcangetintoaman'seyesorintothespaceship'sinstruments．Ifanyoftheinstrumentsisblocked,theastronautsmayhavetroublegettingsafelyhome．
Asastronautstravelonlongerspacetrips,hemusttaketimetosleep．Anastronautcanfithimselftohisseatwithakindofseatbelt．Or,ifhewantsto,hecansleepinasleepingbagwhichisfixedinplaceunderhisseat．Butbecarefulhemustputhishandsunderthebeltwhenhegoestosleep．Thisisbecauseheisreallyafraidthathemighttouchoneofcontrolsthatisn'tsupposedtobetoucheduntillater．
Whywouldastronautscovereachbiteoffoodinspace? A．Becausesmallpiecesoffoodwouldfalldowntothefloor
B．Becauseweightlesspiecesoffoodmightmaketroublewhentheytravelaround
C．Becausetheyhaven'tenoughfoodforlongertrips
D．Becauseastronautsdon'twanttowastefood
参考答案：
答案解析：