The correct option is B In the winter of 618 CE on the banks of river Narmada
As North India reverted to small republics and small monarchical states ruled by Gupta rulers after the fall of the prior Gupta Empire, Harsha united the small republics from Punjab to central India, and their representatives crowned him king at an assembly in April 606 giving him the title of Maharaja.
Harsha established an empire that brought all of northern India under his control. The peace and prosperity that prevailed made his court a centre of cosmopolitanism, attracting scholars, artists and religious visitors from far and wide. The Chinese traveller Hieun Tsang visited the court of Harsha, and wrote a very favourable account of him, praising his justice and generosity.
Pulakeshin II defeated Harsha on the banks of Narmada in the winter of 618-619 CE. Pulakeshin entered into a treaty with Harsha, with the Narmada River designated as the border between the Chalukya Empire and that of Harshavardhana.