Assertion : A hollow metallic closed container with small opening maintained at a high temperature can act as a source of black body radiation. Reason : All metals act as black body radiator.

• A

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

  Ifboth assertion and reason are true but reason is not the correct explanation of assertion.
• Correct answer
  C

  If assertion is true but reason is false.
• D

  If both assertion and reason are false.

Hence, the correct answer is option: 'C'.