Whenyouconnectanexternalmonitortoyourportablecomputer，thesameimageappearsonbothmonitors.Youneedtodragawindowfromonemonitortotheother.Whatshouldyoudo？（）

A.Changethedisplaysettingtoextendthedesktop. B.IntheMicrosoftWindowsMobilityCenterwindow，turnonthePresentationSettingsfeature. C.Configuretheexternalmonitorastheprimarydisplayandthebuilt-inmonitorasthesecondarydisplay. D.Changethesecondarydisplayresolutionsettingstomakethemequaltoorlessthantheprimarydisplayresolutionsettings.