The correct answer is D. Ashoka.
Ashoka was the third emperor of the Mauryan Empire, reigning from 272 to 232 BCE. He is known for his military conquests, as well as his Buddhist reforms. After the Kalinga War, Ashoka renounced violence and adopted Buddhism. He promoted non-violence, vegetarianism, and religious tolerance. He also built many Buddhist stupas and monasteries.
Samudra Gupta was the grandson of Chandra Gupta Maurya and the founder of the Gupta Empire. He was a powerful ruler who conquered much of India. He is known for his military prowess and his patronage of the arts.
Bindusara was the second emperor of the Mauryan Empire. He was the son of Chandra Gupta Maurya and the father of Ashoka. He was a powerful ruler who expanded the Mauryan Empire.
Chandragupta Maurya was the founder of the Mauryan Empire. He was a powerful ruler who united much of India. He is known for his military prowess and his administrative reforms.
All of these rulers were important figures in Indian history. However, only Ashoka adopted Jainism in his last days.