Assertion : Anode of Coolidge tube gets heated up at time of emission of `X` - rays .
Reason : The anode of Coolidge tube is made of a material of high melting point.
A. If both assertion and reason are true and the reason is the correct explanation of the assert ion.
B. If both assertion and reason are true but reason is not the correct explanation of the assertion.
C. If assertion is true but reason is false.
D. If the assertion and reason both are false