叶酸可用于治疗
D
叶酸的应用。甲氨蝶呤、乙胺嘧啶、甲氧苄啶等是叶酸对抗剂，其作用是抑制二氢叶酸还原酶，故这些物质造成的巨幼红细胞性贫血应用叶酸无效，需要甲酰四氢叶酸钙治疗；叶酸制剂适用于妊娠期巨幼红细胞性贫血。
完型填空(本大题共10小题，每小题1分，共10分)从选项中选择一个最适合短文的选项，错选、多选或未选均无分。
Joggingisbecomingoneofthe___21___growingactivitiesinthenation.Morepeoplearestartingjogeachyear.This,however,isarecentoccurrence.Itwasnotlongago__22____joggerswereraresight.Somepeoplethoughtthattheylookedquitestrange.As__23____peoplebeganjoggingthesightofthembecamemorecommon.Therearemanyreasons___24___apersontotakeupjogging.First,itisagoodformofexercise.Thisis__25____itinvolvestheuseofmanypartsofthebody.Theexercisingoftheheartisofgreatbenefit.Thisisoneofthemostimportantpartsofthehumanbody.Iftheheartdoesnotgettheneededexercise,seriousproblemscanoccur.___26___reasonforjoggingisforenjoyment.___27___beinggoodforpeople,itcanalsobeverymuchfun.Partofthefunofjoggingcomesfromtheopportunityitprovidesformeetingotherpeoplewhoenjoyit.One___28___thatshouldbeconsidered___29___apersontakesupjoggingasaformofexerciseofenjoymentisthatitisnotforeveryone.Peopleshouldfirstcheck30theirdoctorsandbepreparedtofindanotherformofexerciseifjoggingisnotrecommended.
21.A.fastestB.quickestC.mostD.best
22.A.whenB.whileC.thatD.as
23.A.manyB.thoseC.moreD.the
24.A.ofB.withC.forD.in
25.A.thatB.whyC.reasonableD.because
26.A.AB.OtherC.TheotherD.Another
27.A.ExceptB.ExceptforC.BesidesD.Regardlessof
28.A.matterB.eventC.thingD.occurrences
29.A.ofB.thatC.whatD.when
30.A.outB.overC.onD.with
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