Explanation:

The question asks about a river basin that covers an area of 860,000 sq km and spans 11 Indian states. Below are the options and their relevance:

- Option 1: Mahanadi basin

- Primarily an east-central Indian river.

- Covers a smaller area compared to others.

- Option 2: Ganga basin

- One of the largest river basins in India.

- Covers an area of approximately 860,000 sq km.

- Spans across 11 Indian states.

- Provides water and fertile soil crucial for agriculture.

- Option 3: Indus basin

- Mostly in Pakistan, with some parts in India.

- Not as large in India as the Ganga basin.

- Option 4: Brahmaputra basin

- Significant river basin, largely in northeastern India.

- Smaller area within India compared to the Ganga basin.

Thus, the Ganga basin is the correct answer as it spans 11 Indian states and covers an area of 860,000 sq km.