"to which nucleotide base are methyl groups added during the process of dna methylation? "

Methylation occurs on cytosine and adenine nucleotide bases.  Methylation of Cytosine occurs with a high affinity, especially in the CpG islands. Methylation happens at the 5’ carbon in the pyrimidine ring to form methyl-cytosine through the addition of a methyl group.

The answer is option a

It has been around since 1858 so b. false