Question: Which of the following changes in a gamete is most likely to lead to a heritable change in a protein?
A: Deleting two nucleotides from the middle of an intron
B: Deleting two nucleotides immediately upstream of a gene promoter
C: Inserting two nucleotides in the genome at the beginning of a codon
D: Adding two nucleotides to the poly(A) tail of an mRNA
Please eliminate two incorrect options first, then think it step by step and choose the most proper one option.