Answer:
A. Alternative mRNA Splicing
Explanation:
The primary transcript of eukaryotes has introns and exons. The post-transcriptional modification includes splicing of introns and joining of exons to form a mature mRNA.
A single gene can specify two or more related proteins due to the process of alternative splicing of mRNA wherein exons are removed and joined in various combinations which in turn serve as the template for different proteins.
For example, if a primary transcript has 7 exons, the mature mRNA may have all 7 exons or some of them in various combinations. The resultant mRNAs with different combinations of exons would specify different proteins.