Which of the following king of ancient India has been referred to as "Piyadarshi"?

Ashoka

The correct answer is Option 4- Ashoka

The king of ancient India who has been referred to as "Piyadarshi" is Ashoka.

Piyadarshi is a Sanskrit word that means "beloved of the gods." It was a title that was used by Ashoka in his inscriptions to describe himself. Ashoka was a great patron of Buddhism, and he is credited with spreading Buddhism throughout Asia. He was also a wise and benevolent ruler, and he is considered to be one of the greatest emperors in Indian history.

The other options are :

Bindusara: He was also known as "Amitraghata," which means "Slayer of Foes."

Bimbisara is also sometimes referred to as "Seniya", "Seniya Bimbisara", or Shrenika" .

Chandragupta Maurya: He is sometimes referred to as "Sandrocottus" in Greek accounts.