Photoshop中在使用仿制图章工具时，虽然有一个正确的取样点，但在使用此工具操作后，无法得到需要复制的图像，造成此现象的原因可能是下列哪几项。()

在photoshop6中允许一个图象的显示的最大比例范围是多少（）

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

如何设定图象的白点

Photoshop中当前图像中存在有一个选择区域，但“编辑”菜单中的“填充”命令无法被激活，其原因可能是下列哪几项。()