The third law of thermodynamics states that:. a. the entropy of the universe equals the sum of the entropy of system and that of the surroundings.
b. the entropy of the universe is constant.
c. the entropy is zero at 0 K for a perfect crystal.
d. the entropy of the universe is increasing.
e. the absolute entropy of a substance decreases with increasing temperature.

C

Explanation:

The third law of thermodynamics states that at absolute zero temperature, the entropy of a perfect crystal is zero. In other words, as the temperature of a system approaches zero, the entropy also approaches a constant value.

The law only holds true only if the crystal has minimal energy and only exist in one state. The entropy becomes zero as the temperature also becomes zero only for a perfect crystal. Otherwise, the law refuses to hold.

The correct option is, therefore, C.

increased stability in the completion of fluorine's outer shell.