The correct answer is 18.

• There are18 Biosphere reserves in India.
• Biosphere reserves are areas of terrestrial and coastal ecosystems promoting solutions to reconcile the conservation of biodiversity with its sustainable use.
  • They are internationally recognized, nominated by national governments, and remain under the sovereign jurisdiction of the states where they are located. 
• They often include one or more National Parks and/or preserves, along with buffer zones that are open to some economic uses. Protection is granted not only to the flora and fauna of the protected region, but also to the human communities who inhabit these regions, and their ways of life.
• First Biosphere Reserve: Nilgiri Biosphere Reserve (Est. 1986)
• Largest Biosphere Reserve: Gulf of Mannar
• Smallest Biosphere Reserve: Panna

 There are 18 biosphere reserves in India:

• Cold Desert, Himachal Pradesh
• Nanda Devi, Uttrakhand
• Khangchendzonga, Sikkim
• Dehang-Debang, Arunachal Pradesh
• Manas, Assam
• Dibru-Saikhowa, Assam
• Nokrek, Meghalaya
• Panna, Madhya Pradesh
• Pachmarhi, Madhya Pradesh
• Achanakmar-Amarkantak, Madhya Pradesh-Chhattisgarh
• Kachchh, Gujarat (Largest Area)
• Similipal, Odisha
• Sundarban, West Bengal
• Seshachalam, Andhra Pradesh
• Agasthyamala, Karnataka-Tamil Nadu-Kerala
• Nilgiri, Tamil Nadu-Kerala (First to be Included)
• Gulf of Mannar, Tamil Nadu
• Great Nicobar, Andaman & Nicobar Island