Answer:
If temperature in an experiment is allowed to change then it is the variable quantity. Hence the answer is option C.
Step-by-step explanation:
Variable quantity is defined as a quantity which keeps on changing with respect to time. In the above question the temperature was allowed to change hence it becomes a variable quantity.
The increase and decrease of temperature could affect the experiment. Sometimes temperature can work as a catalyst to an experiment. And sometimes it works as a poison or it inhibits an experiment.
Whereas a constant quantity is defined as a quantity whose value does not change with respect to time.