The correct answer is (b), Bhagwati Charan Vohra.
Bhagwati Charan Vohra was a revolutionary who was associated with the Hindustan Republican Association (HRA). He was the author of the book ‘The Philosophy of the Bomb’, which was published in 1925. The book is a collection of essays on the philosophy of violence and revolution. Vohra argues that violence is a necessary tool for achieving social and political change. He also discusses the ethics of violence and the role of the individual in the revolutionary struggle.
The other options are incorrect. Bhagat Singh was a revolutionary who was also associated with the HRA. He was executed by the British government in 1931. Chandrashekar Azad was another revolutionary who was associated with the HRA. He was killed in an encounter with the British police in 1931. Ram Prasad Bismil was a revolutionary who was associated with the HRA. He was executed by the British government in 1927.