Which of the following statements regarding heavy water are correct?1. It is extensively used as a moderator in nuclear reactors2. It cannot be used in an exchange reaction to study the reaction mechanism3. The viscosity of heavy water is relatively smaller than of ordinary water4. The dielectric constant of heavy water is smaller than that of ordinary water Select the correct answer using the code given below:

• A. 1 and 2
• B. 2 and 3
• C. 3 and 4
• D. 1 and 4