阅读理解阅读理解阅读下列短文，从每题所给的A、B、C、D四个选项中，选出最佳选项。Elephantsdon'tforgetatleast,female(雌性的)elephantsdon't.Elephantfamiliesarematriarchal.

阅读理解阅读理解

阅读下列短文，从每题所给的A、B、C、D四个选项中，选出最佳选项。

Elephantsdon'tforgetatleast,female(雌性的)elephantsdon't.Elephantfamiliesarematriarchal.Andthesocialknowledgegainedbytheoldestfemalesisthekeytoafamilygroup'ssurvival(生存),accordingtoastudypublishedinAprilbyKarenMcComb,abiologistatSussexUniversityinEngland.

Elephantsannouncetheirpresencebymakingadeep,longsound,apracticereferredtoascontactcalling(联络呼叫).Anunfamiliarcallmaymeanthatanelephantfromoutsidethefamilygroupisnearby.Astrangercancausetrouble,interruptingfeedingordisturbingtheyoung.Soanelephantmatriarchsignalsthefamilytogatheraroundher;thentheyalllifttheirtrunksintheairtosmelltheunfamiliarcaller.Falsealarmscandisturbthegroupandtaketimeandenergyawayfromfeeding,sosurvivalmaydependinpartongettingitright.

WorkingwithCynthiaMoss,whofoundedtheAmboseliElephantResearchProjectinKenya30yearsago,McCombtestedthesocialknowledgeof21Amboselielephantfamilieswithmatriarchs27to67yearsold.Sheplayedrecordingsofcontactcallstoeachfamilyandfoundthattheoldestmatriarchsweremuchbetteratpickingoutunfamiliarcalls.Infact,agroupwithamatriarchinherfiftieswasseveralthousandtimesmorelikelytoformintoagroupuponhearinganunfamiliarcontactcallthanwhenhearingafamiliarcall.However,familieswithyoungermatriarchswerelessthantwiceaslikelytogathertogetheruponhearinganunfamiliarcontactcallascomparedwithafamiliarcall.Andtheygatheredtogetheralot.Moreover,thesocialknowledgeofoldermatriarchstranslatedintofavourableresults:Familieswitholdermatriarchsproducedmorebabyelephantsineachfemale-reproductiveyear.

Thisfindingshowshowdifficultitistoprotecttheoldestmembersofelephantfamilies.Aselephantsage,theycontinuetogrowlarger,asdotheirmuchwantedtusks(象牙).Sotheolderandwiseramatriarchis,thegreaterthechanceshewillbekilled.About800,000elephantshavebeenkilledbypeopleinthepast20years.

1．Whatdoestheunderlinedword“matriarch”mean?

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A．Anoldmemberofanelephantfamily.

B．Afemaleheadofanelephantfamily.

C．Awiseelephant.

D．Ala