Introduction:
The man wants to buy Hilsa fish to win the challenge. Hilsa fish is a popular and highly prized fish in many countries, especially in Bangladesh and India. It is known for its delicious taste and unique flavor. The man is motivated to buy Hilsa fish due to the challenge and the reputation it has gained.

Explanation:
- The challenge: The man wants to buy Hilsa fish because he is participating in a challenge where the goal is to cook the best dish using Hilsa fish. It is likely a cooking competition or a friendly challenge among friends. The man wants to showcase his culinary skills and win the challenge by preparing a delicious dish using Hilsa fish.

- Popularity and discussion: Another reason why the man wants to buy Hilsa fish is because everyone is talking about it. Hilsa fish is highly sought after and often a topic of conversation among food enthusiasts. Its unique taste and popularity have created a buzz, making the man curious to try it and be a part of the discussion.

- Price reduction: It is not mentioned in the question that the price of Hilsa fish has gone down. Therefore, this option can be ruled out as the reason for the man's desire to buy Hilsa fish.

- Pleasing his wife: The man's intention to buy Hilsa fish is not specifically mentioned as an attempt to please his wife. While it is possible that he wants to prepare a special meal for his wife using Hilsa fish, this reason is not mentioned in the question. Therefore, option D can be ruled out as well.

Conclusion:
In conclusion, the man wants to buy Hilsa fish to win the challenge. The challenge and the reputation of Hilsa fish as a delicious and highly prized fish motivate him to participate and showcase his culinary skills. The popularity of Hilsa fish and the conversations surrounding it also contribute to his desire to try it.

Gopal want to buy the hilsa Because the king has challenged him to bring the hilsa no one should ask him anything about Hilsa fish . so to win the challenge he Bring the hilsa fish