RecentlymoreandmorebigcitiesinChinaarehavingheavysmog（雾霾）．ThereisapopularjokeaboutitontheInternet，"Thelongestdistanceintheworldisnotbetweenlifeanddeath，butbetweenyouandmewhenIholdyourhandinthestreetbutcannotseeyourface．"
Airpollutionisoneofthecausesoflung（肺）cancer．Whatshallwedotokeephealthyinthissituation？Trytorememberthefollowingadvice：
▲Reduceoutdooractivities．
▲Ifyouhavetogooutside，remembertowearamask．
▲Drinkmorewateradayandhavefreshfood．
▲Washhandsandfaceafteroutdooractivities．
▲Keepindoorenvironmentclean．
46．Theunderlinedword"mask"means"___"inChinese．
A．帽子
B．手套
C．口罩
47．Whatisoneofthecausesoflungcanceraccordingtothisarticle？___
A．Smoking．
B．Drinking．
C．Airpollution．
48．Thewriteradvisespeopletoreduceoutdooractivitiesbecause___．
A．heavysmogisbadforhealth
B．outdooractivitiesaretooboring
C．theydon'twanttogoout
49．Thewriterthinksweshould___everydayinordertokeephealthy．
A．drinkenoughwater
B．havefreshfood
C．bothAandB
50．WhichstatementisTRUEaccordingtothepassage？___
A．Airpollutioncanmakepeopleblind．
B．We'dbetterwashhandsandfacebeforegoingoutside．
C．Weshouldstayindoorasmuchaspossible．