Which One of the Following Statements MOST Accurately Describes Methylation

Which one of the following statements MOST accurately describes methylation?

A) Methyl groups are most often added to cytosines adjacent to guanine bases in or near the promoter sequence, increasing the probability of gene expression.
B) Methyl groups are most often added to cytosines adjacent to guanine bases in or near the promoter sequence, decreasing the probability of gene expression.
C) Methyl groups are most often added to adenine-thymine base pairs because they are held by only two hydrogen bonds, and this increases the probability of gene expression.
D) Methyl groups are most often added to guanine-cytosine base pairs because they are held by three hydrogen bonds, and this decreases the probability of gene expression.
E) Methyl groups are added to most bases in the promoter region of a specific gene so that RNA polymerase and its associated proteins will bind more efficiently.