The correct answer is A. Gaur.
The gaur is a wild ox native to the Indian subcontinent and Southeast Asia. It is the largest bovine species in the world, with males weighing up to 1,800 kilograms (4,000 lb). Gaurs are herbivores and live in herds of up to 50 individuals. They are an important part of the ecosystem, as they help to control the population of other animals.
The gaur was declared the state mammal of Goa in 2012. This was done in recognition of the importance of the species to the state’s ecosystem. Gaurs are found in several protected areas in Goa, including the Bhagwan Mahavir Wildlife Sanctuary and the Mollem National Park.
The other options are incorrect. The elephant is the state animal of Assam, the Asiatic lion is the state animal of Gujarat, and the tiger is the national animal of India.