B and C are correct - A is incorrect as natural selection affects any generation of species. D is also incorrect as any species population change in an ecosystem inevitably affects another, even if it isn't a predator-prey relationship.
I think the answer is b, because cartilage is what helps with flexibility in tissues....
Vibrissae, more commonly known as whiskers, are sensory hair
that generally have a tactile sense, which is equivalent to skin. They grow on
most mammals except monotremes (duck-billed platypus and echidnas) and humans,
though humans still have remnants of the muscles once associated with vibrissae
in their upper lips. Vibrissae serve a number of purposes: such as sense of
touch; detection of danger, air and water currents, and movements of other
animals; and the locating of food.
The spleen. It acts as sort of a filter for your blood. :)
I think c (it makes getting water easier and and quicker for the cactus
