Manually， you set the consumer group of all of the newly created users to MYDB_GRP. You want the users to be able to change their consumer groups as per the application requirement. What was the first step that was needed in the process to achieve this objective？（）

A. The user must have been granted the DBA role.
B. The user must have been granted the switch privilege as a part of a role.
C. The user must have been granted the Resource Manager administrator privilege.
D. The user must have been granted the switch privilege by using the DBMS_RESOURCE_MANAGER_PRIVS package.