AUniversitycustomerhasaBladeCenterHfullypopulatedwithLS21Blades，asingleAMM，andfourpowermodules.TheBladeCenterhasbeenrunningflawlesslyforthreemonths.Onedayanadministratordiscoversthattheycannotviewvideoonblades9-12eitherlocallyorremotelyeventhoughtheystillappeartoberunning.Thevideoworksonalloftheotherblades.Whichofthefollowingisthecauseofthevideoproblem？（）
A.Apowermodulehasfailedandthereisnotenoughpowertoseevideoonallblades.
B.MUX3ontheBladeCenterbackplanehasfailed.
C.AfirmwareupdateisrequiredontheAMM.
D.AsecondAMMisrequiredtoviewvideoonblades9-14.
参考答案：B
