In simple inheritance,

Question $28$ options:

A$)$

phenotypic characteristics are determined by multiple alleles.

B$)$

phenotypic characteristics are determined by a single pair of alleles.

C$)$

phenotypic characteristics are determined by the action of two genes.

D$)$

phenotypic characteristics are determined by the genes on the Y chromosome.

E$)$

phenotypic characteristics are controlled by regulator genes on a chromosome other than the one that has the structural genes.