The correct answer is: c) Nepenthes khasiana (Pitcher Plant)
A flowering plant species endemic to Mizoram (found nowhere else) is Nepenthes khasiana, also known as the Khasi pitcher plant. It is a carnivorous plant that grows in the Khasi Hills of Meghalaya and Mizoram in northeastern India. It is the largest of all pitcher plants, with pitchers that can reach up to 1 meter in height. The pitchers are modified leaves that are used to trap insects. The insects are attracted to the sweet nectar produced by the plant, and once they enter the pitcher, they are unable to escape. The plant then digests the insects and uses the nutrients to grow.
The other options are not endemic to Mizoram. Rhododendron is a genus of flowering plants that is found in the Northern Hemisphere. Begonia davisii is a species of begonia that is found in the Himalayas. Rafflesia is a genus of flowering plants that is found in Southeast Asia.