This is a typical monohybrid cross involving a single gene B.
Both parents are purebreeding or homozygous i.e. have identical alleles for the specified trait. Hence, in a cross between the two, all the offsprings will be heterozygous (Bb) i.e. possess different alleles for the trait (See attached image).
N.B: A genotype is the genetical make up of an organism.
Since the genotypes of all the possible offsprings will be Bb, there is none that will possess the same genotype as any of the parent. Hence, the percentage is 0% i.e. 0/4 × 100
A molecule is made of more than one atom of differing elements that can be simplified while an element cannot be simplified because it is only one atom of one type of element.