Explanation:

 Justification: Biosphere is that part of the earth in which living organisms exist or which supports life. Please note we are not talking about the “biosphere reserve”.Protected areas, just like any large ecosystem, are a significant part of our biosphere that is established to protect our flora, fauna and their habitats. So, the most appropriate analogy is option A where a tree is one among many (species both plant and animals) in a forest. Option D: This in invalid as biosphere is much larger than any protected area on earth. Two celestial bodies may be of the same size.