The temporary hardness of water is due to

How is the oxygen atom surrounded in ice?

The velocity of neutrons in a nuclear reactor is slowed down by

The chemical name of calgon is

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

Permanent hardness cannot be removed by