ThefirsttimeIremembernoticingthecrossingguardwaswhenhewavedtomeasIdrovemysontoschool.He__1__mewithapuzzle-allbecausehewavedtomelikesomeonedoes__2__seeingaclosefriend.Abig,__3__smileaccompaniedhiswave.Forthene

　　ThefirsttimeIremembernoticingthecrossingguardwaswhenhewavedtomeasIdrove

　　mysontoschool.He__1__mewithapuzzle-allbecausehewavedtomelikesomeonedoes

　　__2__seeingaclosefriend.Abig,__3__smileaccompaniedhiswave.Forthenextfewdays

　　Itriedto__4__hisfacetoseeifIknewhim.Ididn't.Perhapshehad__5__meforsomeoneelse.

　　BythetimeIcontentedmyselfwiththe__6__thatheandIwerestrangers,weweregreeting

　　eachotherwarmlyeverymorninglikeoldfriends.

　　()2.A.onB.fromC.duringD.about

　　()4.A.studyB.recognize

　　为什么2题选a,详细分析每个选项

　　4题为什么选a,不选b,ab有什么区别