Genes is found in the DNA. It decides a specific characteristic. Genes can transform and take two or more option structures and these structures are called Alleles. Presently allele happens in an altered spot in a chromosome and in people we have two arrangements of chromosomes.
There are 46 chromosomes in the human. 23 from the dad, 23 from the mother = 46 chromosomes.
I believe the correct response is D. Need a living host cell to reproduce.
The effect of geographic isolation is that the two populations are subjected to different selection (pressures) and geographic conditions. The conditions in the two areas, if different, will produce different alleles in that species and will be selected for, where genetic differences will gradually accumulate between the two different populations.
In time, enough genetic differences will occur so that the two populations will no longer interbreed. Then, by definition, they have become different species.