Question related to Change Control System

Hello,
Please help me by answering this question:-
 
If you would like to find out who will be approving changes in your project deliverables and documentation, you can
refer to the ________
A) Change Control System
B) Project Management Plan
C) Organization Chart
D) Resource Assignment Matrix
 
Answer is A.
Please explain why it is A and not D.
 
Thanks

Here Key words are "approving changes". these are like changes added later. any changes should go through CCB. all these info will be defined in Change Control System.

Resource Assignment Matrix --> This is related to resoucres used in project execuion stage.

 PMBOK definition for RAM , definitons of Change control , change control board, change control system