Auserwiththeuseridof’joe’isunabletorshfromSYSTEMAtoSYSTEMBwithouthavingtoretypetheirpassword，buttheycanrshfromSYSTEMBtoSYSTEMA.Nootherusersareexperiencingthesameissue.Bothsystemshavea/home/joe/.rhostsfilethatcontaintheproperreferencestotheotherhost.The/home/joe/.rhostsfilesonbothSYSTEMAandSYSTEMBareownedbyuserid’joe’.Whichofthefollowingisthemostlikelycauseofthisproblem？（）
A.User’joe’isspecifiedinthe/etc/nologinonSYSTEMA
B.User’joe’isspecifiedinthe/etc/nologinonSYSTEMB
C.Thefilepermissionsonthe/home/joe/.rhostsfileonSYSTEMAiscorrect.
D.Thefilepermissionsonthe/home/joe/.rhostsfileonSYSTEMBisincorrect.