The correct answer is: a) East Champaran.
The Valmiki Tiger Reserve is located in the East Champaran district of Bihar, India. It is one of the largest tiger reserves in India, covering an area of over 3,800 square kilometers. The reserve is home to a variety of wildlife, including tigers, leopards, elephants, rhinos, and deer. It is also a popular tourist destination, with visitors coming to see the wildlife and the beautiful scenery.
The other options are incorrect.
Option b, West Champaran, is a district in Bihar, India. It is located to the west of East Champaran.
Option c, Patna, is the capital of Bihar, India. It is located to the south of East Champaran.
Option d, Gaya, is a city in Bihar, India. It is located to the south of East Champaran.