如下内容来自华研外語《考研英語真題集训》，觉得它解释得比很好懂，分享一下。
全国硕士硕士入学统一考试
英語（一）试題
SectionIUseofEnglish
Directions:
Readthefollowingtext.Choosethebestword(s)foreachnumberedblankandmarkA,B,CorDontheANSWERSHEET.(10points)
Thoughnotbiologicallyrelated,friendsareas“related”asfourthcousins,sharingabout1%ofgenes.Thatis1astudy,publishedfromtheUniversityofCaliforniaandYaleUniversity
Thestudyisagenome-wideanalysisconducted31,932uniquesubjectswhich4pairsofunrelatedfriendsandunrelatedstrangers.Thesamepeoplewereusedinboth5.
While1%mayseem6,itisnotsotoageneticist.AsJamesFowler,professorofmedicalgeneticsatUCSanDiego,says,“Mostpeopledonoteven7theirfourthcousinsbutsomehowmanagetoselectasfriendsthepeoplewho8ourkin.”
Thestudy9foundthatthegenesforsmellweresomethingsharedinfriendsbutnotgenesforimmunity.Whythissimilarityexistsinsmellgenesisdifficulttoexplain,fornow.10,astheteamsuggests,itdrawsustosimilarenvironmentsbutthereismore11it.Therecouldbemanymechanismsworkingtogetherthat12usinchoosinggeneticallysimilarfriends13“functionalkinship”ofbeingfriendswith14!
Oneoftheremarkablefindingsofthestudywasthatthesimilargenesseemtobeevolving15thanothergenes.Studyingthiscouldhelp16whyhumanevolutionpickedpaceinthelast30,000years,withsocialenvironmentbeingamajor17factor.
Thefindingsdonotsimplyexplainpeople’s18tobefriendthoseofsimilar19backgrounds,saytheresearchers.ThoughallthesubjectsweredrawnfromapopulationofEuropeanextraction,carewastakento20thatallsubjects,friendsandstrangersweretakenfromthesamepopulation.Theteamalsocontrolledthedatatocheckancestryofsubjects.
1.A.what B.why C.how D.when
2.A.defended B.concl