Passage OneQuestions 21 to 25 are based on the following passage. During the early years o

PassageOne

Questions21to25arebasedonthefollowingpassage.

Duringtheearlyyearsofthiscentury，wheatwasseenastheverylifebloodofWesternCanada.Whenthecropsweregood，theeconomywasgood；whenthecropsfailed.therewasdepression.Peopleoncitystr eetswatchedtheyieldsandthepriceofwheatwithalmostasmuchfeelingasiftheyweregrowers.Themarketingofwheatbecameanincreasinglyfavoritetopicofconversation.

Warsetthestageforthemostd ramaticeventsinmarketingthewesterncrop.Foryearsfarmersmistr ustedspeculative(投机的)grainsellingascarriedonthroughtheWinnipegGrainExchange.Wheatpricesweregenerallylowintheautumn，butfarmerscouldnotwaitformarketstoimprove.Ithadhappenedtoooftenthattheysoldtheirwheatsoonafterharvestwhenfarmdebtswerecomingdue，onlytoseepricesrisingandspeculatorsgettingrich.Onvariousoccasions，producergroupsaskedforfirmercontr ols，butgovernmentshadnowishtobecomeinvolved，atleastnotuntilwartimewheatpricesthreatenedtorunwild.

Anxioustocheckinflation(通货膨胀)andrisinglivingcosts，thefederalgovernmentappointedaboardofgrainsupervisors(监视员)tohandledeliveriesfromthecropsof1917and1918.GrainExchangetr adingwassuspended，andfarmerssoldatpricesfixedbytheboard.Tohandlethecropof1919，thegovernmentappointedthefirstCanadianWheatBoard，withfullauthoritytobuy，sell.andsetprices.

Theauthorusestheterm“lifeblood”toindicatethatwheatwas______.

A.difficulttoproduceinlargequantities

B.susceptibletomanyparasites(寄生虫)

C.essentialtothehealthofthecountr y

D.expensivetogatherandtr ansport