The number of major histocompatibility (MHC) protein combinations possible in a given population is enormous. However, an individual in that diverse population has a far more limited array of MHC molecules because .

The correct answer is "each of the MHC genes has a large number of alleles, but each individual only inherits two for each gene".

Explanation:

In normal conditions, an individual has only two different alleles for a given gene: one inherited from his mother and the other from his father. However, this does not mean that among humans, there are only two different alleles for each gene. The major histocompatibility (MHC) genes are a clear example of this, since there are multiple combinations for each MHC class. For instance, there are 40 very similar alleles only for the HLA-B27 subtype.

the answer to your question is:

c. complementary base-pairing

answer: ice crystals in air

the water from the water body or another source of water gets evaporated as water vapor as an effect of heat on water. these water vapor rises in the upper layers of the earth atmosphere under high atmospheric pressure. the atmospheric pressure of these water molecules starts to decrease due to the effect of cold air. the invisible water vapor condenses into visible water droplets and ice crystals.these ice crystals and water droplets being less denser than the surrounding air floats on air as clouds.