What makes an acid (or base) strong or weak?

if a substance have more hydrogen ion than the other it is called as strong acid

it is determined by the colour it gives to the pH scale

some examples may include: HCl, H2SO4

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.