单项选择题
A. Roles.CreateRole(listName)User.IsInRole(listName)
B. Roles.CreateRole(listName)Roles.AddUserToRole(userName, listName)
C. Roles.RoleExists(listName)Roles.AddUserToRole(userName, listName)
D. Roles.RoleExists(listName)User.IsInRole(listName)