下列关于对象 -关系数据库的叙述中,哪些是正确的?

A、对象-关系数据库以关系模型为基础
B、对象-关系数据库中的表都符合第一范
C、对象-关系数据库中的表都符合第一范式
D、对象-关系数据库提供继承机制
E、对象-关系数据库安全性好,达到美国TCSEC和TDI的B1级标准
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正确答案:

ACD

答案解析:

暂无解析

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下列哪项是引起胸痛的胸壁疾病

A、 肺癌 
B、 肋间神经痛 
C、 
D、 胸膜炎
E、胸膜肿瘤 

Thismountainrangehasmanyhigh_____andfertilevalleys.

A、peaks
B、hills
C、phase
D、pink

Passage2

Questions6to10arebasedonthefollowingpassage:

Thefoodweeatseemstohaveprofoundeffectsonourhealth.Althoughsciencehasmadeenormousstepsinmakingfoodmorefittoeat,ithas,atthesametime,mademanyfoodsunfittoeat.Someresearchhasshowntat40percentofcancerisrelatedtothedietaswell,especiallycancerofthecolon.Differentculturesatemorepronetogetcertainillnessesbecauseofthefoodthatischaracteristicinthesecultures.Thatfoodisrelatedtoillnessisnotanewdiscovery.In1945,governmentresearchersrealizedthatnitratesandnitrites,commonlyusedtopreservecolorinmeats,andotherfoodadditives,causedcancer.Yetthesecarcinogenicadditivesremaininourfood,anditbecomesmoredifficultallthetimetoknowwhichthingsonthepackaginglabelsofprocessedfoodarehelpfulorharmful.Theadditivesthatweeatarenotallsodirect.Farmersoftengivepenicillintobeefandpoultry,andbecauseofthis,penicillinhasbeenfoundinthemilkoftreatedcows.Sometimessimilardrugsareadministeredtoanimalsnotformedicinalpurposes,butforfinancialreasons.Thefarmersaresimplytryingtofattentheanimalsinordertoobtainahigherpriceonthemarket.AlthoughtheFoodandDrugAdministration(FDA)hastriedrepeatedlytocontroltheseprocedures,thepracticescontinue.

6.Howhassciencedoneadisservicetomankind?

A.Becauseofscience,mostofthefoodsweeattodayarecontaminated.

B.Ithascausedalackofinformationconcerningthevalueoffood.

C.Asaresultofscientificintervention,somepotentiallyharmfulsubstanceshasbeenaddedtoourfood.

D.Thescientistshavepreservedthecolorofmeats,butnotofvegetables.

7.Whatarenitratesusedfor?

A.Theypreservesflavorinpackagedfoods.

B.Theypreservethecolorofmeats.

C.Theyaretheobjectsofresearch.

D.Theycausetheanimalstobecomefatter.

8.TheFDAhastriedrepeatedlytocontrol.

A.theattempttofattentheanimals

B.theattempttocuresickanimals

C.theusingofdrugstoanimals

D.theusingofadditivestopreservethedoloroffood

9.Theword“carcinogenic”meansmostnearlythesameas.

A.trouble-makingB.color-retaining

C.money-savingD.cancer-causing

10.WhichofthefollowingstatementsisNOTtrue?

A.Drugsarealwaysgiventoanimalsformedicalreasons.

B.Someoftheadditivesinourfoodareaddedtothefooditselfandsomearegiventothelivinganimals.

C.Researchershaveknownaboutthepotentialhazardsofthefoodadditivesforoverthirty-fiveyears.

D.Foodmaycausefortypercentofcancerintheworld.

脐带包含

A、脐静脉1条,脐动脉1条
B、脐静脉1条,脐动脉2条
C、脐静脉2条,脐动脉1条
D、脐静脉2条,脐动脉2条

正常胎动为

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