Eutrophication occurs when excess nutrients are supplied to a region, leading to an algae bloom and ultimately A. ocean acidification.
B. coral bleaching.
C. ocean deoxygenation.
D. overfishing

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.

the answer is true when observing or determining population size, a direct observation is use, in which each organism is counted in a population or in an area. one benefit of this measure is that you get the exact population count but it will take a long time to  determine  the  size  of a  population.