What is the difference in potential between two charges called

Its potential is taken as zero potential. Thus the positively charged conductor has more positive potential than the earth. A  negatively charged conductor has negative potential less than that of the earth. The electric potential difference between two points in an electric circuit is the work done in moving a unit positive charge from one point to the other.

multiple allele inheritance is traits controlled by more than 2 alleles (ex: pigeons having 3 alleles of one gene govern their feather color).   so the answer is a.