The reagent involved in the Clemmensen reduction of carbonyl compound is

Zinc amalgam and HCl

The correct answer is Option (2) → Zinc amalgam and HCl

Clemmensen Reduction:

• Used to convert carbonyl compounds (aldehydes/ketones) → alkanes
• Reagent: Zn(Hg) / conc. HCl (zinc amalgam in hydrochloric acid)

Quick comparison of options:

1. Sodium amalgam and HCl → Used in Birch reduction (not Clemmensen)
2. Zinc amalgam and HCl → Clemmensen reduction → Correct
3. KOH and ethylene glycol → Wolff-Kishner reduction (alternative to Clemmensen)
4. Zinc amalgam and HNO₃ → Not used (HNO₃ is oxidizing, not reducing)