Answer D is correct. When an EXECUTE AS statement is run, the execution context of the session is switched to the specified login or username. sp_change_users_login maps an existing database user to a SQL Server login. Auto_Fix links a user entry in the sysusers table in the current database to a SQL Server login of the same name. Update_One links the specified user in the current database to an existing SQL Server login. The username and login must be specified. The password must be NULL or not specified.
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