D

Mono- and dioxygenases insert one or both atoms of O₂ into a substrate respectively [Harayama, 1992, PMID 1444267]. Cytochrome P450 mono-oxygenases—classic oxygenases—carry out steroid hydroxylations [Yoshimoto, 2016, PMID 27339894]. Drug carboxylation, however, is mediated by biotin-dependent or other carboxylases and does not require oxygenases [Schneider, 2024, PMID 39572135]. Therefore option D is the incorrect statement.