Answer: Option (A) is the correct answer.
Explanation:
A conductor that conducts heat and electricity very effectively at very low temperature is known as a super conductor.
There occurs no resistance in a super conductor.
For example, magnesium diboride, mercury, lead etc are super conductors.
Since, super conductors only work at temperature which are lower than their critical temperature this makes them less useful.
Therefore, we can conclude that a drawback to superconductors is that they perform well only at very low temperatures.
