In your database，the LDAP_DIRECTORY_SYSAUTH initialization parameter has been set to YES and the users who need to access the database as DBAs have been granted SYSDBA enterprise role in Oracle Internet Directory （OID）. SSL and the password file have been configured. A user SCOTT with the SYSDBA privilege tries to connect to the database instance from a remote machine using the command：$ SQLPLUS scott/tiger@DB01 AS SYSDBA where DB01 is the net service name. Which authentication method would be used first？（）

A. authentication by password file
B. authentication by using certificates over SSL
C. authentication by using the Oracle Internet Directory
D. authentication by using the local OS of the database server