The correct answer is option 1, Defence Minister. The Defence Acquisition Council is headed by the Defence Minister of a country. This council is responsible for making decisions and providing policy guidelines for the acquisition of defence equipment and services by the armed forces. It plays a crucial role in the procurement process and ensures that the defence capabilities of the country are strengthened.

Option 2, Defence Secretary, is not the correct answer as the Defence Secretary is a bureaucrat who supports the Defence Minister and works in the Ministry of Defence but does not head the Defence Acquisition Council.

Option 3, Chief of the Integrated Defence Staff, is also not the correct answer. While the Chief of the Integrated Defence Staff plays an important role in coordinating and integrating the activities of the three defence services, they do not head the Defence Acquisition Council.

Option 4, Director General (Acquisition), is also not the correct answer. The Director General (Acquisition) is a position within the Ministry of Defence and assists the Defence Minister in matters related to defence acquisition, but does not head the Defence Acquisition Council.

Therefore, the correct answer is option 1, Defence Minister.