The answer is D.
An endothermic reaction involves absorbing heat whereas an exothermic involves releasing heat.
Assuming the white phenotype is recessive. white: gg
I think the gray mouse is Gg because the offspring were pretty equally distributed in terms of color. See the punnet square below.
g g
G| Gg Gg
g| gg gg
If the Gray phenotype is recessive, then gray: ww but only if white is Ww because its about 50% chance for both.
