The correct answer is option 4, which states that the senior-most Chief of Staff acts as the chairman of the Chiefs of Staff Committee.

The Chiefs of Staff Committee is a group that consists of the Chiefs of the three armed forces of India - the Army, Navy, and Air Force. This committee is responsible for advising the government on important military matters and coordinating the activities of the armed forces.

In terms of hierarchy, the senior-most Chief of Staff is considered the most experienced and highest-ranking officer among the three chiefs. Therefore, it is logical for this officer to assume the role of the chairman of the committee. This position allows the senior-most chief to provide leadership and guidance to the committee, facilitating effective decision-making and coordination among the armed forces.

Contrary to popular belief, the President of India, who is the commander-in-chief of the armed forces, does not act as the chairman of the Chiefs of Staff Committee. Similarly, the Prime Minister and the Defence Minister also do not hold this position.