Explanation:

Let’s break it down:

- Hindustan Petroleum: Used to hold a stake, but not anymore.

- Bharat Petroleum: This is the one you’re looking for. Bharat Petroleum Corporation Limited (BPCL) currently holds the major stake in Numaligarh Refinery Limited (NRL) after Indian Oil and Oil India restructured their holdings.

- Chennai Petroleum: This one mainly operates in Tamil Nadu. No direct connection to Numaligarh.

- Reliance Petrochemicals: Private sector giant, but not involved with NRL at all.

So, your answer is option 2—Bharat Petroleum.