Assertion: Refining of petroleum involves fractional distillation.
Reason: Fractional distillation involves repeated distillation. Repeated distillation means repeated heating.

a) Both assertion and reason are true, and the reason is the correct explanation of the assertion.
b) Both assertion and reason are true, but the reason is not the correct explanation of the assertion.
c) Assertion is true, but the reason is false.
d) Assertion is false, but the reason is true.