The World Network of Biosphere Reserves is a program by UNESCO that aims to promote the conservation of biodiversity and sustainable development. Biosphere reserves are selected based on their unique ecosystems and ability to serve as learning sites for sustainable development. Option 4, Corbett, is not included in the World Network of Biosphere Reserves.
Option 1, Sunderbans, is a biosphere reserve located in West Bengal and is included in the World Network of Biosphere Reserves. Option 2, Gulf of Mannar, is a biosphere reserve located in Tamil Nadu and is included in the World Network of Biosphere Reserves. Option 3, Nandadevi, is a biosphere reserve located in Uttarakhand and is also included in the World Network of Biosphere Reserves. Therefore, Corbett is the correct answer as it is not included in the network.