Here is the question.

Management by objectives works only if:
A. It is supported by management
B. The rules are written down
C. Project does not impact the objectives
D. Project includes the objectives in the Project Charter

The answer is A. and the only explanation that is provided is "The best answer is that it needs management support".

Can anyone here shed some light on WHY A is the answer and not the other choices? And this is the first time I have heard the term "Management by Objectives". Is this mentioned anywhere in the PMBOK?