The correct answer is: A. Atharvaveda
The Atharvaveda is one of the four Vedas, the sacred texts of Hinduism. It is a collection of hymns, spells, and incantations, and is believed to have been composed between 1200 and 1000 BCE. The Atharvaveda is the only Veda that mentions the region of Bihar by the name of ‘Kikat’.
The Rigveda is the oldest Veda, and is believed to have been composed between 1500 and 1200 BCE. It is a collection of hymns to the Vedic gods, and does not mention the region of Bihar.
The Satpath Brahmana is a Brahmana text, which is a type of Hindu scripture that is a commentary on the Vedas. It is believed to have been composed between 800 and 600 BCE. The Satpath Brahmana does not mention the region of Bihar.
The Bhagwati Sutra is a Hindu text that is a commentary on the Brahma Sutras. It is believed to have been composed between 400 and 200 BCE. The Bhagwati Sutra does not mention the region of Bihar.