For some conditions, having one mutated copy of a gene in each cell is advantageous,
while having two mutated copies causes disease. The best-studied example of this
phenomenon is sickle cell disease: Having two mutated copies of the HBB gene in each
cell results in the disease, but having only one copy provides some resistance to
malaria. This disease resistance helps explain why the mutations that cause sickle cell
disease are still found in many populations, especially in areas where malaria is
prevalent.
What mechanism of evolution is this?
Founders effect
Mutations
Geographic Isolation
coevolution

producers: apple trees, potatoes, carrots, grains, acorns, cabbage, grass, corn, lettuce

consumers: deer, mice, rabbits, chickens, squirrels, horses, worms, cows

predators: eagles, frogs, wolves, owls

c. earths continental crust is thicker than its lithosphere.

because, the lithosphere is the outermost layer of the earth/ 100 km thick and is defined by its machanical properties.the lithosphere contains oceanic and continental crust that varies in age and thickness across locations and geologic time. the lithosphere is the coolest layer of the earth in terms of temperature. the term lithosphere should not be confused with the use of "geosphere" which is used to indicate all of earth systems, including the atmosphere, hydrosphere   and biosphere. the surface of the earth can be divided into the continental crust and the oceanic crust.   the continental crust is made mostly of granite while the oceanic crust is made of basalt. the average thickness of the continental crust is 25 miles and the average thickness of the oceanic crust is 5 miles.   three types of rock, igneous, sedimentary, and metamorphic, make up the surface of the earth. that's why 3 option is preferable.

multiple allele inheritance is traits controlled by more than 2 alleles (ex: pigeons having 3 alleles of one gene govern their feather color).   so the answer is a.

occluded front i think