The correct answer is: c) Southwest Punjab.
The Indus River system is a major river system in South Asia. It is the longest river in Pakistan and the second-longest river in India. The Indus River system originates in the Tibetan Plateau and flows through India and Pakistan before emptying into the Arabian Sea. The Indus River system is a major source of water for irrigation and drinking water in Pakistan and India.
The Indus River system primarily drains Southwest Punjab. Southwest Punjab is a region in Pakistan that is located in the southwest of the country. Southwest Punjab is bordered by the provinces of Sindh and Balochistan to the south, the province of Khyber Pakhtunkhwa to the north, and the Indian state of Jammu and Kashmir to the east. Southwest Punjab is a major agricultural region in Pakistan. The Indus River system is a major source of water for irrigation in Southwest Punjab.
The other options are incorrect because they do not accurately describe the region of Punjab that is primarily drained by the Indus River system. Option a) Northeast Punjab is incorrect because the Indus River system does not primarily drain Northeast Punjab. Option b) Central Punjab is incorrect because the Indus River system does not primarily drain Central Punjab. Option d) Southeast Punjab is incorrect because the Indus River system does not primarily drain Southeast Punjab.