The correct answer is option 'D' - Subarnarekha River.

Explanation:
The Rourkela Steel Plant, located in the state of Odisha (formerly known as Orissa), is one of the largest steel plants in India. It is operated by the Steel Authority of India Limited (SAIL) and plays a significant role in the country's steel production.

The Subarnarekha River is the river that provides water to the Rourkela Steel Plant. Here's an explanation of why this river is the source of water for the plant:

1. Importance of water in the steel industry:
- Water is an essential resource in the steel manufacturing process.
- It is used for various purposes, including cooling, cleaning, dust suppression, and steam generation.
- Steel plants require a continuous and reliable water supply to ensure efficient production.

2. Location of the Rourkela Steel Plant:
- The Rourkela Steel Plant is situated in the Sundargarh district of Odisha.
- It is strategically located near the confluence of three important rivers - the Subarnarekha River, the Koel River, and the Sankha River.

3. Choice of the Subarnarekha River as the water source:
- Among the three rivers near the steel plant, the Subarnarekha River is the primary source of water for the Rourkela Steel Plant.
- The Subarnarekha River is a perennial river that originates in the Chhotanagpur plateau of Jharkhand.
- It flows through the states of Jharkhand, West Bengal, and Odisha before emptying into the Bay of Bengal.
- The river has a relatively good flow throughout the year, making it a dependable source of water for industrial purposes.

4. Water supply infrastructure:
- The Rourkela Steel Plant has set up water intake structures on the Subarnarekha River to extract water for its operations.
- The water is then treated and supplied to various units within the plant.
- Adequate infrastructure, including pipelines and storage tanks, is in place to ensure a continuous and reliable water supply.

In conclusion, the Subarnarekha River provides water to the Rourkela Steel Plant in Odisha. Its perennial flow and proximity to the plant make it an ideal source of water for the steel manufacturing process.

The Subarnarekha River provides water to the Rourkela Steel Plant in Orissa (Option D).