Correct Option: C

TDT do not require a template as it adds N-nucleotides to the variable exons during antibody gene recombination. It functions by catalysing the addition of nucleotides to the 3’ terminus using 3’ – overhang as the substrate. Also it can act independently on blunt or recessed 3’ ends. It is expressed in immature, pre- B , pre –T lymphoid cells and uses cobalt as cofactor, also Mg/Mn ²⁺ presence in-vitro. It is used in adding nucleotides labelled with radioactive isotopes in TUNEL assay (terminal deoxynucleotidyl transferase dUTP Nick End Labelling). ​