$Assertion :$In an adiabatic process, change in internal energy is equal to work done on or by the gas in the process.

$Reason :$The temperature remains constant in an adiabatic process.

if both assertion and reason are true but reason is not the correct explanation of assertion

If both assertion and reason are true and reason is the correct explanation of assertion.

if both assertion and reason are false

if assertion is true but reason is false.