不允许记录中出现重复索引值的索引是

A、主索引
B、主索引、候选索引、普通索引
C、主索引和候选索引
D、主索引、候选索引和唯一索引
查看答案
正确答案:

C

答案解析:

暂无解析

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以下有关PNG文件格式的描述正确的是

A、PNG可以支持索引色表和优秀的背景透明,它完全可以替代GIF格式
B、PNG-24格式支持真彩色,它完全可以替代JPEG格式
C、PNG是未来WEB图象格式的标准,它不仅是完全开放的而且支持背景透明和动画等
D、由于PNG是一种新开发的文件格式,它需要浏览器软件的支持才可以正常浏览

在使用选区范围生成切片时:

A、由于切片为矩形,所以只能使用矩形选区生成切片
B、如果图象上有多个互相分离的选区,则将根据每个选区范围分别生成多个切片
C、由于经过羽化的选区没有明确的边界,所以无法通过它生成切片
D、以上答案都不对

下列操作不能删除当前图层的是:

A、将此图层用鼠标拖至垃圾桶图标上
B、在图层面板右边的弹出菜单中选删除图层命令
C、直接按delete键
D、直接按esc键

Thefoodweeatseemstohaveprofoundeffectsonourhealth.Althoughsciencehasmadeenormousstepsinmakingfoodmorefittoeat,ithas,atthesametime,mademanyfoodsunfittoeat.Someresearchhasshownthatperhapseightypercentofcancerisrelatedtothedietaswell,especiallycancerthecolon.Differentculturesaremorepronetocontractcertainillnessesbecauseofthefoodthatischaracteristicinthesecultures.Thatfoodrelatedtollnessisnotanewdiscovery.In1945,governmentresearchersrealizedthatitratesandnitrites,commonlyusedtopreservecolorinmeats,andotherfooddditives,causedcancer.Yet,thesecarcinogenicadditivesremaininourfood,nditbecomesmoredifficultallthetimetoknowwhichthingsonthepackginglabelsofprocessedfoodarehelpfulorharmful.Theadditiveswhichweeatarenotallsodirect.Farmersoftengivepenicillintobeefandpoultry,andbecauseofthis,penicillinhasbeenfoundinthemilkoftreatedcows.Sometimessimilardrugsareadministeredtoanimalsnotformedicinalpurposes,butforfinancialreasons.Thefarmersaresimplytryingtofattentheanimalsinordertoobtainahigherpriceonthemarket.AlthoughtheFoodandDrugAdministration(FDA)hastriedrepeatedlytocontroltheseprocedures,thepracticescontinue.

48.Whatisthemaintopicofthepassage?

A.Foodandourhealth

BFoodandadditives

C.Foodandcancer

DFoodandculture

49AllofthefollowingstatementsaretrueEXCEPT_______.

AFortypercentofcanceriscausedbyproblemsrelatedtofood.

BResearchershaveknownaboutthepotentialdangeroffoodadditivesformanyyears

C.Weeatsomeofthefoodadditivesdirectlyandsomeindirectly

DDrugsarealwaysgiventoanimalsformedicinalpurposes

50.Whydofarmersgivedrugstotheiranimals?

A.tospeedupthegrowthofanimals

BTomaketheanimalsfatter

Ctomaketheanimals’meatfittoeat

DTomaketheanimals’meatrichinnutrients

51.Itcanbeinferredfromthepassagethat_________.

Ascientisthavemadeallthefoodfittoeat

Bonlyinrecentyearshavepeoplefoundthatthefoodisrelatedtoone’sillness

Callkindsofcancerarerelatedtothediet

Dsomeadditivesareharmfultoourhealth

52.Theword“this”inthesecondsentenceofparagraph2mostprobablyrefersto__________.

Afarmer

Bpenicillin

Cbeefandpoultry

Dthefactthatfarmersoftengivepenicillintoabeef

当图象是何种模式时,所有的滤镜都不可以使用(假设图象是8位/通道)

A、CMYK
B、灰度
C、多通道
D、索引颜色
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