The printed key (c) is wrong: it pairs P with catalase and R with P-450. P-450 is the R–H hydroxylase and catalase disproportionates H₂O₂, which gives (b).
Explanation
P (R–H + O₂ + 2H⁺ + 2e⁻ → R–OH + H₂O, monooxygenation of a C–H bond) – cytochrome P-450 (II). Q (four-electron reduction of O₂ to water, coupled to proton pumping) – cytochrome c oxidase (III). R (disproportionation 2H₂O₂ → 2H₂O + O₂; the table's 'O₁' is a misprint for O₂) – catalase (IV). S (glycine → serine) is the remaining pair, coenzyme B₁₂ (I). Only option (b) has P-II, Q-III, R-IV, S-I. The printed key (c) would make catalase the hydroxylase and P-450 the peroxide-disproportionation enzyme, which is wrong. Answer: (b).