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.

the correct answer is: b. pantala flavescens, because these organisms would have a high level of genetic variation due to sexual reproduction.  

because involves two organisms (parents) whose genetic material combines, sexual reproduction leads to genetic variation in new generations of offspring. the offspring is an unique organism, with new genome, more protected with the higher ability to adapted. this process is fundamental to evolution.