Statements about heavy water are given below :
A. Heavy water is used in exchange reactions for the study of reaction mechanisms.
B. Heavy water is prepared by exhaustive electrolysis of water.
C. Heavy water has higher boiling point than ordinary water.
D. Viscosity of H₂O is greater than D₂O.

Heavy water made from the heavy isotope of hydrogen. The rate of cleavage of D-O bond is lesser than the rate of cleavage of O-H bond. This results in the slow down the mechanism and easy to study it.

Ratio of D₂O and H₂O in the ordinary water is 1:6000. Exhaustive repeated electrolysis of water in the presence of 3% NaOH produce deuterium oxide or heavy water. 

Heavy water has a higher molecular mass than the ordinary water. As more is the molecular mass of compound, more is the Van der Waal forces results in the high boiling point of the compound. Therefore, the boiling point of D₂O is higher than H₂O. 

Viscosity of a liquid depends on the molecular mass of liquid and the intermolecular forces present in the liquid. The additional neutron in deuterium enhances the intermolecular forces in heavy water. Because of the high molecular mass and high intermolecular forces, viscosity of heavy water is larger than the ordinary water.