Explanation:

National Parks are protected areas established by the government to conserve wildlife and biodiversity. The number of National Parks varies significantly across different states and Union Territories of India. \nOption A, 'Assam', is incorrect. Assam is known for its rich biodiversity and has several important National Parks, such as Kaziranga and Manas, but it does not hold the record for the maximum number. \nOption B, 'Meghalaya', is incorrect. Meghalaya has a few National Parks, but their number is not the highest among Indian states/UTs. \nOption C, 'Arunachal Pradesh', is incorrect. Arunachal Pradesh, despite its vast forest cover, does not have the maximum number of National Parks. \nOption D, 'Andaman and Nicobar Islands', is the correct answer. This Union Territory is renowned for its unique insular biodiversity and boasts the highest number of National Parks in India, with a total of nine National Parks. These include the Mahatma Gandhi Marine National Park, Rani Jhansi Marine National Park, and Saddle Peak National Park, among others. Their high number reflects the critical importance of conserving the unique ecosystems and endemic species found in these islands.