The correct answer for this question is option 2: Competition Commission of India.

In India, mergers and acquisitions of firms are regulated by the Competition Commission of India (CCI). The CCI is a statutory body that ensures fair competition and market efficiency in the Indian economy. Its main objective is to prevent anti-competitive practices, promote sustainable competition, and protect the interests of consumers.

Option 1, National Manufacturing Competitiveness Council, is incorrect. While this council was established to enhance the competitiveness of the Indian manufacturing sector, it does not have the mandate to regulate mergers and acquisitions.

Option 3, Securities and Exchange Board of India, is also incorrect. The SEBI is a regulatory body that oversees the securities market and protects the interests of investors. While it plays a crucial role in regulating capital markets, it is not directly responsible for regulating mergers and acquisitions.

Option 4, Department of Industrial Policy and Promotion, is also incorrect. Although this department plays a vital role in formulating and implementing policies related to industrial development and foreign direct investment, it does not specifically regulate mergers and acquisitions.

In conclusion, the correct regulatory body for mergers and acquisitions in India is the Competition Commission of India (CCI).