Explanation:

Antecedent drainage refers to a river that has maintained its course through a mountain range or other geological formations that have risen subsequent to the formation of the river. In other words, the river has flowed across the uplifted land and maintained its original course.

Out of the given options, the river that does not represent antecedent drainage is the Subansiri River. Let's understand why:

Chenab River:
- The Chenab River flows through the Indian states of Jammu and Kashmir and Himachal Pradesh, as well as the Pakistani provinces of Punjab and Khyber Pakhtunkhwa.
- It originates from the confluence of the Chandra and Bhaga rivers in Himachal Pradesh.
- The Chenab River has maintained its course through the Himalayas, indicating that it is an example of antecedent drainage.

Sutlej River:
- The Sutlej River flows through the Indian states of Himachal Pradesh and Punjab, as well as the Pakistani province of Punjab.
- It originates from the Rakshas-Tal near Mansarovar Lake in Tibet.
- The Sutlej River has also maintained its course through the Himalayas, indicating that it is an example of antecedent drainage.

Ravi River:
- The Ravi River flows through the Indian states of Himachal Pradesh and Punjab, as well as the Pakistani provinces of Punjab and Khyber Pakhtunkhwa.
- It originates from the Bara Bhangal area in Himachal Pradesh.
- The Ravi River has maintained its course through the Himalayas, indicating that it is an example of antecedent drainage.

Subansiri River:
- The Subansiri River is a tributary of the Brahmaputra River and flows through the Indian state of Arunachal Pradesh.
- It originates from the Tibetan Plateau near the Mansarovar Lake.
- However, the Subansiri River does not maintain its course through the Himalayas. Instead, it flows through the Subansiri district of Arunachal Pradesh.
- Therefore, the Subansiri River does not represent antecedent drainage.

In conclusion, out of the given options, the Subansiri River does not represent antecedent drainage.