Explanation:

- The 750-MW Rewa ultra-mega solar power project is located in Madhya Pradesh.

- Madhya Pradesh is known for its investment in renewable energy projects.

- The project represents a significant step in harnessing solar energy in India.

- Andhra Pradesh, although supportive of solar energy, does not host the Rewa project.

- Uttar Pradesh has its own solar initiatives but is not related to Rewa.

- Himachal Pradesh focuses more on hydroelectric power due to its geography.

- Arunachal Pradesh is largely involved in hydro projects, not solar.

- Correct Answer: Madhya Pradesh.