Option 1 -> Bindusara was Ashoka's father and the second emperor of the Mauryan dynasty, not its founder.
Option 2 -> Chandragupta Maurya established the Mauryan Empire around 321 BCE and was its founding emperor.
Option 3 -> Samudragupta belonged to the Gupta dynasty, not the Mauryan dynasty.
Option 4 -> Harshvardhana ruled the Vardhana dynasty in the 7th century CE, unrelated to the Mauryan lineage.
Hence, Option 2: Chandragupta Maurya -> He founded the Mauryan Empire with the help of Chanakya, establishing one of the largest empires in ancient India. His grandson Ashoka the Great later expanded and strengthened this dynasty, becoming its most celebrated ruler -> correct