Botany，thestudyofplants，occupiesapeculiarpositioninthehistoryofhumanknowledge.Formanythousandsofyearsitwastheonefieldofawarenessaboutwhichhumanshadanythingmorethanthevaguestofinsight.ItisimpossibletoknowtodayjustwhatourStoneAgeancestorsknewaboutplants，butfromwhatwecanobserveofpreindustrialsocietiesthatstillexist，adetailedlearningofplantsandtheirpropertiesmustbeextremelyancient.Thisislogical.Plantsarethebasisofthefoodpyramidforalllivingthings，evenforotherplants.Thehavealwaysbeenenormouslyimportanttothewelfareofpeople，notonlyforfood，butalsoforclothing，weapons，tools，dyes，medicines，shelter，andagreatmanyotherpurposes.TribeslivingtodayinthejunglesoftheAmazonrecognizedliterallyhundredsofplantsandknowmanypropertiesofeach.Tothembotany，assuch，hasnonameandisprobablynotevenrecongnizedasaspecialbranchofknowledgeatall.

Unfortunately，themoreindustrializedwebecomethefartherawaywemovefromdirectcontactwithplants，andthelessdistinctourknowledgeofbotanygrows.Yeteveryonecomesunconsciouslyonanamazingamountofbotanicalknowledge，andfewpeoplewillfailtorecognizearose，anapple，oranorchid.WhenourNeolithicancestors，livingintheMiddleEastabout10，000yearsago，discoveredthatcertaingrassescouldbeharvestedandtheirseedsplantedforricheryieldsthenextseason，thefirstgreatstepinanewassociationofplantsandhumanswastaken.Grainswerediscoveredandfromtheflowedthemarvelofagriculture-.cultivatedcrops.Fromthenon，humanswouldincreasinglytaketheirlivingfromthecontrolledproductionofafewplants，ratherthangettingalittlehereandalittletherefrommanyvarietiesthatgrewwild―andtheaccumulatedknowledgeoftensofthousandsofyearsofexperienceandintimacywithplantsinthewildwouldbeginfadeaway.

Accordingtothepassage，whyhasgeneralknowledgeofbotanybeguntofade

A.Peoplenolongervalueplantsasausefulresource.

B.Botanyisnotrecognizedasspecialbranchofscience.

C.Researchisunabletokeepupwiththeincreasingnumbersofplants.

D.Directcontactwithavarietyofplantshasdecrease

正确答案：D