Onecauseofthecurrentfoodcrisisisdrought．FoodpricesarehighinpartbecauseofdryweatherinplacesasfardistantasSpainandAustralia．Aroundtheworldtheamountoflandaffectedbydroughthasdoubledinthepastthirtyyears．Andscientistsconcernedaboutclimatechangebelieveitwillcausemoredroughtinmanyareasinthefuture.
Alotofresearchisgoingintoeffortstodevelopdrought-resistantcrops．Oneprojectinvolvestobaccoplantsgeneticallyengineeredtokeeptheirleavesduringwatershortages．Theychosetobaccobecauseithasbigleaves．Alsoitgrowsfastandhasstructuralsimilaritieswithsomeotherplants.
Theresearchersdidanexperimentwithtwogroupsoftobaccoplants．Theyworkedwithasetofnormalplantsandasetoftransgenicplants．Thesehadageneaddedtointerferewiththebiologicalcausesofleaflossduringdrought.
Theresearchersputalltheplantsinagreenhousetogrowundernormalconditionsforfortydays．Thenforfifteendaysafterthattheplantsdidnotreceiveanywater.
Thenormalplantslosttheirgreencolor．Finallytheylosttheirleaves．Buttheresearcherssaythetransgenicplantskepttheirleavesandtheircolor.
Afterthefifteendrydaysalltheplantswerewateredagainforaweek．Thetransgenicplantsreturnedtonormalgrowthandtheirseedproductionwasclosetonormal．Buttheotherplantsalldied.
Inadditiontheresearchersfoundthattheplantscouldsurviveononlythirtypercentofthenormalamountofirrigationwater．Yieldlosswasminortheysaid.
Thefindingsappearedlate2007intheProceedingsoftheNationalAcademyofSciences．TheUniversityofCaliforniahasappliedforpatentprotectionforthetechnology.
TheresearchersexpecttomoveforwardwithfieldtestingofthetransgenictobaccoinlateAugust．Theyhopeforsimilarresultswithcropsliketomatoesricewheatandcotton.
71．ItcanbeinferredfromParagraph1that_______
A．theamountoflandaffectedbydroughthasdoubledinthepastthirtyyearsintheworld
B．droughtistheonlycausetoleadtothecurrentfoodcrisis.
C．foodpriceswillbehigherinthefuturewiththedroughtareasextending
D．foodpriceshasnothingtodowiththe
