A. The Sex.
This is because of the last pair int he Karyotype. which is used to determine the sex of a human (XX or XY). In this case because there are 2 long chromosomes, this is a female (XX), but if there was one long and one short, that would be a male (XY). This can also be seen if the chromosome types are labeled like in this diagram. <span />
The answer is mechanical weathering
Important factor defining the desert biomes is its tendency to lose water by evaporation, and this potential for water loss exceeds the annual rainfall and defines what organism can live in there.
Natural selection doesn't favor traits that are somehow inherently superior. Instead, it favors traits that are beneficial (that is, help an organism survive and reproduce more effectively than its peers) in a specific environment. Traits that are helpful in one environment might actually be harmful in another.
(one again, I hope this helps ^^)
