The correct answer is (a) Bodh Gaya.
Bodh Gaya is a town and a notified area committee in Gaya district in the Indian state of Bihar. It is famous as the place where Gautama Buddha attained enlightenment under the Bodhi tree. The Mahabodhi Temple, a UNESCO World Heritage Site, was built at the spot where Buddha attained enlightenment.
The river Niranjana flows through Bodh Gaya. It is a tributary of the Phalgu River.
The other options are incorrect.
(b) Kusinagara is a town in the Indian state of Uttar Pradesh. It is the place where Gautama Buddha attained Mahaparinirvana, or final nirvana.
(c) Lumbini is a town in the Lumbini Zone of Nepal. It is the birthplace of Gautama Buddha.
(d) Rishipattana is a town in the Indian state of Uttar Pradesh. It is the place where Gautama Buddha gave his first sermon.