Which of the following is not a phase I reaction -: (A) Oxidation, (B) Reduction, (C) Hydrolysis, (D) Conjugation
Answer is D. Phase I reactions →  Oxidation (including hydroxylation), reduction, hydrolysis, cyclization and decyclization.
Phase II reactions → Conjugation reaction (glucuronidation, sulfation, acetylation, methylation, conjugation with glutathione, aminoacid conjugation).