Explanation:

The plot of Swapnavasavadatta is drawn from the romantic narratives about the Vatsa king Udayana and Vasavadatta, the daughter of Pradyota, the ruler of Avanti, which were current in the poet’s time and which seem to have captivated popular imagination. The drama narrates the sorrow of Udayana for his queen Vasavadatta, believed by him to have perished in a conflagration, which was actually a rumour spread by Yaugandharayana, a minister of Udayana to compel his king to marry Padmavati, the daughter of the king of Magadha. It forms, in context, a continuation of his another drama, Pratijnayaugandharayana. 

Swapnavasavadatta is based on the brihatakatha of gunadhya and is referred to in the mahabharata. Bhasa stands pre-eminent for the boldness of his conception, insight into character and for his homely sparking style. He has written about thirteen plays of which the svapna-vasavadatta is reckoned as a masterpiece both in ancient indian and modern criticism.

Hence, option (a) is correct.