A. large population residing on an isolated island
A huge population residing in an isolated setting would likely cause less genetic drift. Certain factors may less affect the population like immigration and mutation.
To view the mitochondria you will need a light microscope. The mitochobdria is to small to see with a light microscope. The organelles are found in tje cheeck of an onion cell bit are to small to see.
B) Both parents are heterozygous. It is clear that Black fur is a dominant trait, so a white mouse is the result of two submissive traits clicking together.