Assertion : At high altitudes , liquids boil at lower temperatures in comparison to that at sea level .
Reason : At high altitudes , atmospheric pressure is low .
A. If both assertion and reason are true and reason is the correct explanation of assertion .
B. If both assertion and reason are true but reason is not the correct explanation of assertion .
C. If assertion is true but reason is false .
D. If both assertion and reason are false .