The correct option is
B Calcutta
Calcutta is not an example of India's ancient town. This is because there is no ancient history associated with the state. Its history is associated and is limited only to the Britisher's time. Calcutta was the capital of British India. It was famous for its river port for trade and commerce with the rest of the world. Further, if we talk about Prayagraj, Patliputra, and Varanasi, these states have an ancient history.
Prayagraj is an ancient town and is also illustrated in the Vedas. It is believed that it is located where Brahma, the Creator of the Universe, attended a sacrificial ritual. Patliputra was an ancient India city originally built by the Magadha Ruler near Ganges River. It became the capital of major powers in ancient India.
Varanasi also was known as Benaras, in the Rig Veda, the city is referred to as Kāśī (Kashi) from the Sanskrit verbal root kaś- "to shine", making Varanasi known as "City of Light. Moreover, according to Hindu mythology, Varanasi was founded by Shiva. Thus, there is no such ancient history associated with Calcutta.