The person who is known as the `Iron Man of India` is Vallabhbhai Patel. Option 1 is the correct answer. Vallabhbhai Patel was one of the key leaders of the Indian independence movement. He played a crucial role in the integration of several princely states into the newly independent India.

Option 2, Bipin Chandra Pal, was also an important figure in the Indian independence movement. He was a prominent nationalist leader and one of the triumvirate with Lala Lajpat Rai and Bal Gangadhar Tilak. However, he is not known as the `Iron Man of India`.

Option 3, Gopal Krishna Gokhale, was a social reformer and political leader who advocated for political reforms and education. However, he is not known as the `Iron Man of India`.

Option 4, Bal Gangadhar Tilak, was a nationalist and freedom fighter who played a significant role in the Indian independence movement. He was known as the `Father of the Indian Unrest`. However, he is not known as the `Iron Man of India`.

In conclusion, the correct answer is option 1, Vallabhbhai Patel, who is known as the `Iron Man of India`.