骨盆的各个平面中，下述哪项是正确的（）

乳牙出齐的年龄是（）

_____youunderstandthisrule，you‘llhavenodifficultyindealingwithsuchproblems.

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.

特发性血小板减少性紫癜的特点描述正确的是（）