Assertion: If your hands come in contact with hot objects (perhaps stove burner, hot plate, hot pan or a hot potato), a reflex causes you to immediately remove your hand before the message from the brain.
Reason: Heat shock reflex arc is polysynaptic and the relay neuron also sends the information to the brain.
Both assertion and reason are correct.
Heat shock reflex arc is polysynaptic in nature and involves a communication to the brain also. It is because of this relay processing that the brain is able to override the reflex response after some time of exposure to the stimulus