It appears that "hidden genetic variation" is responsible forallowing selection to move the average value of a traitbeyond the range of values that the trait displayed in theinitial population. what explicitly, do we mean by "hiddengenetic variation" (where is it hidden? ) and by what meanscan such hidden genetic variation be expressed so thatselection can act upon it?

Selection may be defined as the process of selecting the more favorable species than the less favored one and can adapt in the environment. The selection increase the chances of survival of the organism.

The genetic variation hidden means the variation is not visible in the population and present in the form of heterozygotes in the population. This genetic variation can be expressed by the recombination of the heterozygotes in the population.

poor water quality affects most estuarine organisms, including commercially important fish and shellfish. the pollutants that have the greatest impact on the health of estuaries include toxic substances like chemicals and heavy metals, nutrient pollution (or eutrophication), and pathogens such as bacteria or viruses.

option number one would be youre best option