Who founded the Nanda dynasty of Magadha?

The correct answer is C, Mahapadma Nanda. Mahapadma Nanda overthrew the Shishunagas and founded the Nanda dynasty in the fourth century BCE. The Puranas call him Ekarat, the sole sovereign, and Sarva-kshatrantaka, the uprooter of all kshatriyas, because he destroyed the older ruling houses; he is also described as of low birth, so the Nandas are often called the first non-kshatriya dynasty of Magadha. He built the army and treasury that the Mauryas inherited.

Option A, Shishunaga, founded the earlier Shishunaga dynasty and annexed Avanti. Option B, Kalashoka or Kakavarna, was a Shishunaga ruler and the patron of the Second Buddhist Council at Vaishali. Option D, Dhana Nanda, was the last of the line, the ruler whose army Greek writers describe and whom Chandragupta Maurya and Chanakya overthrew around 322 BCE, but he was not the founder.