The INCORRECT statement(s) about heavy water is (are)
(A) Used as a moderator in a nuclear reactor
(B) Obtained as a by-product in the fertilizer industry
(C) Used for the study of the reaction mechanism
(D) Has a higher dielectric constant than water
Choose the correct answer from the option given below:
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The correct option is D (D) only

Deuterium is the isotope of hydrogen.
Isotopes are used for the study of the reaction mechanism.
Hence, heavy water is also used for the study of reaction mechanism.
In nuclear reactors, heavy water is used a moderator due to its higher boiling point than normal water.
These are also obtaines as by-product in the fertilizer industry.

$D_{2}O$=78.06 (Dielectric constant)
$H_{2}O$=78.39 (Dielectric constant)
The dielectric constant of heavy water is lesser than normal water due to less polarisation in $D_{2}O$. This is beacuse of the heavier deuterium atom.
Thus, statement (d) is incorrect.