In the peppered moth scenarios what is the variation? and the selection?

because of

the correct answer, according to e2020, is the second choice there is an occluded front in region a and a cold front in region b.

the cell is the smallest structural and functional unit of living organisms, which can exist on its own. therefore, it is sometimes called the building block of life. some organisms, such as bacteria or yeast, are unicellular—consisting only of a single cell—while others, for instance, mammalians, are multicellular.