Unit3Protectingourselves课外阅读练习阅读下列短文,从每篇短文后所给各题的四个选项中,选出最佳选项
RecentlytheWorldHealthOrganizationannouncedthatthediseaseofsmallpox(天花)hadalmostbeenwipedoutinmostpartsoftheworld,thankstowidespreadvaccination(种牛痘).Mostpeoplearevaccinatedatleastonceintheirlivesandiftheywishtotravelfromonecountrytoanothertheymustbeabletoprovethattheyhavehadarecentvaccination.Inthiswaythediseasehasbeenpreventedfromspreadingandtodayoneseldomhearsofitatall.Thisismainlybecauseofthegreatdiscoverymadebyavillagedoctor,EdwardJenner,inabout1798whenhepublishedhisreportofhisnewexperimentcalledvaccination(fromtheword“vacca”meaningacow).Jennerdiscoveredthatpeoplewhoworkedwithcattleoftensufferedfromaharmlessdiseasewhichtheycaughtfromthecattle,butthesepeopleneverseemedtogetsmallpox.Soheexperimentedbyputtingthediseaseintoasmall