The correct answer is option 2: The longest serving Chief among the Chiefs of the three services functions as the chairman of the Chiefs of Staff Committee.

To better understand the options, let`s dissect each one:

Option 1: Defence Minister

The Defence Minister is a political position and is in charge of the Ministry of Defence. While the Defence Minister plays a crucial role in the decision-making process for the armed forces, they do not serve as the chairman of the Chiefs of Staff Committee.

Option 2: The longest serving Chief among the Chiefs of the three services

This option is correct. The chairman of the Chiefs of Staff Committee is chosen from among the three Chiefs of the services - the Chief of the Army Staff, the Chief of the Navy Staff, and the Chief of the Air Staff. The one with the longest years of service is appointed as the chairman.

Option 3: The Chief of Integrated Defence Staff

The Chief of Integrated Defence Staff is responsible for promoting jointness and integration among the three services. While this position plays an important role in coordinating efforts between the services, they do not serve as the chairman of the Chiefs of Staff Committee.

Option 4: The Chief of the Army Staff

The Chief of the Army Staff is the senior most military officer