The correct answer is (b) Levees prevent rivers from flooding their banks.
Levees are formed when water pushes the sediments to the side of a river. They serve as a natural barrier and prevents flood. This is very beneficial in terms of human settlement. Levees can be natural or artificial. They prevent water from going into the areas where there is a human settlement (bank of river). They prevent the rivers from flooding cities in a storm surge. If levees are broken the result can be disastrous for the surrounding area.
Heredity increases diversity among organisms by nonrandom mating, which is the preference of the organism to mate with another based on specific characteristics. Nonrandom mating has two forms. Inbreeding is the first form where organisms with the same genotypes will mate with each other resulting in minimal genetic diversity. Outbreeding is the second form where organisms of different genotypes will mate with each other resulting in an increase in genetic diversity. The variation in the heredity of an organism allows it to be more flexible and can also guarantee better survival rate of the population under the given environmental conditions.
