The answer is A. Vikramaditya.
Vikramaditya was a legendary king of Ujjain who is said to have ruled in the 5th century CE. He is often associated with the Gupta Empire, but there is no historical evidence to support this claim.
Chandragupta was the founder of the Mauryan Empire in the 4th century BCE. He is considered one of the greatest rulers in Indian history.
Harshavardhana was the emperor of the Harsha Empire in the 7th century CE. He was a powerful and successful ruler who expanded his empire to include much of northern India.
Samudragupta was the emperor of the Gupta Empire in the 4th century CE. He was a great conqueror who expanded the Gupta Empire to its greatest extent.
Chanakya was a Brahmin scholar and statesman who served as the chief advisor to Chandragupta Maurya. He is considered one of the greatest political thinkers in Indian history.
The word that is different from the rest is Vikramaditya. The other four words are all historical figures who ruled over large parts of India. Vikramaditya, on the other hand, is a legendary figure who is not attested to in any historical records.