单项选择题
A.function changeImage（） {myImage.src = "image2.png"； }
B.function changeImage（） { document.getElementById（"myImage"）.src = "image2.png"； }
C.function changeImage（） { getElementById（"myImage"）.src = "image2.png"； }
D.function changeImage（） { window.getElementById（"myImage"）.src = "image2.png"； }
单项选择题 You create a Web page that contains drop-down menus that are defined by using div tags in the following code. You need to write a JavaScript function that will enable the drop-down menus to activate when the user positions the mouse over the menu title. Which code segment should you use？（）
单项选择题 YouareimplementingaWebpagethatdisplaystextthatwastypedbyauser.YouneedtodisplaytheuserinputintheWebpagesothatacross-sitescriptingattackwillbeprevented.Whatshouldyoudo？（）
单项选择题 YouaredevelopingaWebpage.Theusertypesacreditcardnumberintoaninputcontrolnamedccandclicksabuttonnamedsubmit.Thesubmitbuttonsendsthecreditcardnumbertotheserver.AJavaScriptlibraryincludesaCheckCreditCardfunctionthatreturnsavalueoftrueifthecreditcardappearstobevalid,basedonitschecksum.Youneedtoensurethattheformcannotbeusedtosubmitinvalidcreditcardnumberstotheserver.Whatshouldyoudo?（）
