Explanation:

The Sundaland Biodiversity Hotspot is a region in Southeast Asia, encompassing the Malay Peninsula and the islands of Sumatra, Borneo, Java, and Bali. The Nicobar Islands, an archipelago in the eastern Indian Ocean, are geographically and ecologically considered an extension of the Sundaland hotspot. Option (A) Mizoram and Option (D) Tripura are states in Northeast India and fall under the Indo-Burma Biodiversity Hotspot, which is distinct from Sundaland. Option (C) Lakshadweep Islands are located in the Arabian Sea and are not part of any major biodiversity hotspot in the same classification, though they possess unique marine biodiversity. Thus, the Nicobar Islands are the only option that is part of the Sundaland Biodiversity Hotspot.