JEE Main 26 Feb 2021 Shift 1 Solved Paper

Statement A is true. Heavy water (D2O) is used in exchange reactions as a tracer compound for the study of reaction mechanisms.
e.g. NaOH+D2O⟶NaOD+HDO
Statement B is true. Heavy water is prepared by prolonged exhaustive (multi-stage ) electrolysis of ordinary water (H2O) containing NaOH.
Statement C is true. Heavy water has higher boiling point (374.4K) than ordinary water (373K).
Statement D is false. Because viscosity (in centipoise) of D2O is greater (1.107) than H2O(0.8903).
So, statements A,B and C are correct (option-a).