_____you understand this rule ，you‘ll have no difficulty in dealing with such problems.
A、WhileD
once意思是“一旦”。while“當(dāng)??時(shí)候”;though“雖然”;unless“除非”。“一旦你明白了這個(gè)規(guī)則，處理類似的問題就不困難了。”顯然，d符合句子意思的表達(dá)需要。
Theagriculturalrevolutioninthe19thcenturyinvolvedtwothings：theinventionoflabor-savingmachineryandthedeyelopmentofscientificagriculture.Labor-savingmachinerynaturallyappearedfirstwherelaborwasscarce.“InEurope，”saidThomasJefferson，“theobjectistomakethemostoftheirland，laborbeingabundant：hereitistomakethemostofourlabor，landbeingabundant.”ItwasinAmerica，therefore，thatthegreatadvancesin19thcenturyagriculturalmachineryfirstcame.
Attheopeningofthecentury，withtheexceptionofacrudeplowfarmerscouldhavecarriedpracicallyalloftheexistingagriculturalimplementsontheirbacks;by1860，mostofthemachineryinusetodayhadbeendesignedinanearlyform.Themostimportantoftheearlyinventionswastheironplow.Asearlyas1790CharlesNewboldofNewJerseyhadbeenworkingontheideaofacast-ironplowandspenthisentirefortuneinintrodueinghisinvention.Thefarmers，however，wouldhavenoneofit，claimingthattheironpoisonedthesoilandmadetheweedsgrow.Nevertheless，manypeopledevotedtheirattentiontotheplow，untilin1869JamesOliverofSouthBend，Indiana，turnedoutthefirstchilled-stillplow.?
1.Whatisthemaintopicofthepassage?
a.Theneedforagriculturaladvancestohelpfeedagrowingpopulation.
b.Thedevelopmentofsafermachinesdemandedbythelabormovement.
c.Machinerythatcontributedtotheagriculturalrevolution.
d.NewJerseyasaleaderintheagriculturalrevolution.
2.Theexpression“makethemostof”inLine4isclosestinmeaningtowhichofthefollowing?
a.getthebestyieldfrom
b.raisethepriceof
c.makefulluseof
d.earnalivingon
3.WhichofthefollowingcanbeinferredfromwhatThomasJeffersonsaid?
a.EuropewaschangingmorequicklythanAmerica.
b.EuropehadgreaterneedoffarmmachinerythanAmericadid.
c.Americawasfinallyrnningoutofgoodfarmland.
d.TherewasashortageofworkersonAmericanfarm.
4.Itcanbeinferredthatthewaord“here”inLine4refersto_____.a.Europe
b.America
c.NewJersey
d.Indiana
5.Whatpointistheautormakingbystatingthatfarmerscouldcarrynearlyalltheirtoolsontheirbacks?
a.Farmershadfewtoolsbeforetheagriculturalrevolution
b.Americansweretraditionallyself-reliant.
c.Lifeonthefarmwasextremelydifficult.
d.Newtoolsweredesignedtobeportable.
Thosepeople_____ageneralunderstandingofthepresentsituation.
Icanspeak_____German.
Hedrovefastandarrivedanhour_____ofschedule.
Thedriverpulled_____atthetrafficlights.
