If temperature in an experiment is allowed to change, it is the
a. control
b. hypothesis
c. variable
d. conclusion

If temperature in an experiment is allowed to change then it is the variable quantity. Hence the answer is option C.

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.