One of the selective advantages of dark skin color in the tropics is that it reduces

The correct option is (A).

Explanation:

It is true that folate is necessary in men so as to maintain the normal production of the sperm.Folate is also known as Vitamin B-9.Folate is present in Foods, vegetables,eggs, fruits and legumes.Folate is needed in the body so as to make the red and white blood cells in the bone marrow.It produces DNA and RNA.It converts carbohydrates into energy.

D.

Natural selection is the differential survival and reproduction of individuals because of the differences in the phenotypic characteristics. It supports the fact that those organisms, which have phenotypic characteristic favorable to survive in the changing environment as compared to other organisms, and these traits will also be passed to the successive generations.

In the given situation, the hummingbirds those have adapted according to the needs, that is deriving nectar from either from short and long tubes nectar. Therefore, two phenotypic characteristics like short beak and long beaks will become dominant trait in the population of humingbirds as the intermediate beak hummingbirds will not be able to feed from either of the flowers.

Therefore, option D. Hummingbirds with shorter or longer beaks can feed from one of the available orchids, but hummingbirds with intermediate beak lengths cannot feed from either is correct.