Answer:
(A) two
Explanation:
A heterodimeric protein consists of two polypeptides (a polypeptide is a chain of amino acids) that differ in amino acid composition, number or order in the chain sequence. Each polypeptide makes a different subunit of the protein.
One gene encodes one polypeptide, so if the protein has two different polypeptides, two genes are required to form this protein.