Explanation:

- Correct Answer: Option 3 - Bhagat Singh

- Bhagat Singh, an Indian revolutionary freedom fighter, wrote the essay "Why I Am an Atheist" in 1930 while imprisoned. In this poignant piece, he articulates his views on atheism and critiques religious orthodoxy, emphasizing rationalism and challenging the belief in divine intervention in worldly matters.

- Option 1: Subhash Chandra Bose

- An influential leader in the Indian independence movement, known for his role in the Indian National Army. He did not write "Why I Am an Atheist."

- Option 2: Khudiram Bose

- A young revolutionary leader known for his involvement in the Indian nationalist movement. He did not write the essay in question.

- Option 4: Madan Lal Dhingra

- An Indian revolutionary known for his assassination of British official William Hutt Curzon Wyllie; he did not author "Why I Am an Atheist."