A is not correct because this needs to be a Calendar resource, not a secondary calendar.
B is not correct because this does not change the fact that others can still see the room.
C is correct because this gives that person the permission to handle booking changes to that room.
D is correct because this removes the visibility of that room to other users on the domain.
E is not correct because this would be a lot of work, with potential for error and angst among the users that booked the room.
Reference:
https://support.google.com/a/answer/1034381?hl=en