Explanation:

- 1. Kosi:

- The Kosi River is not a tributary of the Indus river system.

- ?? It is actually a part of the Ganges river system.

- It flows through Nepal and enters India in Bihar.

- 2. Satluj:

- The Satluj River is a significant tributary of the Indus.

- It flows through India and Pakistan.

- 3. Ravi:

- The Ravi River is another tributary of the Indus.

- It flows along the Indo-Pak border before entering Pakistan.

- 4. Beas:

- The Beas River eventually merges with the Satluj.

- It is also part of the Indus river system.

: Kosi is not a tributary of the Indus river system.