Indicate Which of the Following Enzymatic Activities Corresponds to A

Short Answer

Indicate which of the following enzymatic activities corresponds to A, B, or C in the following schematic drawing of DNA methylation events in the human genome. Your answer would be a three-letter string composed of letters A, B, and C only, e.g. CBA.

( ) DNA demethylating enzyme
( ) Maintenance methyl transferase enzyme
( ) De novo methyl transferase enzyme