BEINGanastronautsoundscool，doesn'tit？Inspace，theygettodosomeprettyamazingthings，likefloatinginzerogravity （重力）．

However，therearealsoplentyofthingsthatastronautscan'tdobecauseoftheirweightlessenvironment，andthat'sverysad．What'sworse，theycan'tevenlettheirsadnessshow-becauseit'simpossibletocryinzerogravity．

Ofcourse，astronautscanstillproducetears．Butcryingismuchmoredifficultinspace，reportedTheAtlanticinJanuary．Withoutgravity，tearsdon'tflowdownwardoutoftheeyesliketheydohereonEarth．Thismeansthatwhenyoucryinspace，yourtearshavenowheretogo-theyjuststicktoyoureyes．

InMay2011，astronautAndrewFeustelexperiencedthisduringoneofhisspacewalks．"Tears，"hesaid，"don'tfalloffofyoureye．Theyjuststaythere．"

Besidesmakingyourvisionunclear，thiscanalsocausephysicalpain．BackonEarth，tearsaresupposedtobringcomforttotheeyes．Butthat'snotthecaseinspace．Thespaceenvironmentdriesoutastronauts'eyes，andwhentearssuddenlywettheeyes，itcancausepainratherthancomfort．"Myrighteyeispainfullikecrazy．"Feusteltoldhisteammateduringthewalk．

Sincegravitydoesn'tworkinspace，astronautsneedsomeextrahelptogetridofthetears．Feustelchosetorubhiseyesagainsthishelmettowipethetearsaway．Anotherchoiceistojustwait-"Whenthetearsgetbigenoughtheysimplybreakfreeoftheeyeandfloataround，"astronautRonParisetoldTheAtlantic．

Therearelotsofsmallthings-thingslikecrying-thatwearesousedtoonEarth．Weusuallytakethemforgranted，untiltheybecomeaprobleminatotallydifferentenvironment，likespace．There，astronautscan'ttalktoeachotherdirectly．Theyalsocan'teatordrinkinnormalways．Theycan'tevenburp （打嗝），becausethereisnogravitytoholdthefooddownintheirstomach．Iftheydoburp，theyjustendupthrowingup （呕吐） everythingintheirstomach，accordingtotheUKNationalSpaceCenter．

Thus，perhapsit'sonlyspaceexplorerswhocanhonestlysay："Gravity，you'rethebest．"

55．Whatcanweconcludefromparagraphs2and3？___

A．Tearsproducedinspacedon'tflowdownward．