This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Biochemistry
5-methylcytosine mutation of DNA (DNA methylation) leads to 
Select and explain. 
A. Deamination to thymine, B. DNA repair, C. Methylation protects the host DNA from cleavage by its own restriction enzyme, D. All of these
D: All of these
Answer: D: All of these 
Explanation: DNA methylation is essential for enthralling a number of the cellular process including transcription, genomic imprinting, developmental regulation, mutagenesis, DNA repair and chromatin organization.
DNA methylation also protects DNA from bacteria's own restriction enzymes.
Deamination of 5-methylcytosine forms thymine, this can result in transition mutation.