​Plants are known to synthesize more than 30,000 terpenoids, involving four stages of biosynthesis. Following are the list of biosynthetic steps (Column X) and the key class of enzymes involved (Column Y):​

​Which of the following is the correct match?​​

Correct option is D

Explanation-

A. Biosynthesis of two basic five-carbon units
→ Refers to synthesis of IPP (isopentenyl pyrophosphate) and DMAPP (dimethylallyl pyrophosphate)
→ Key enzyme: HMG-CoA synthase (in mevalonate pathway)
Correct match: A – iii
B. Repetitive additions of C₅ units
→ These additions create geranyl (C10), farnesyl (C15), and geranylgeranyl (C20) precursors
→ Catalyzed by prenyltransferases
Correct match: B – iv
C. Formation of the basic terpenoid skeletons
→ Cyclization or rearrangement to form monoterpenes, sesquiterpenes, diterpenes, etc.
→ Catalyzed by terpene synthases
Correct match: C – i
D. Modification of terpenoid skeletons
→ Involves oxidation, hydroxylation, epoxidation, etc.
→ Done by P450 monooxygenases
Correct match: D – ii

Final Answer:
A – iii, B – iv, C – i, D – ii (Option d)