Assertion: Static crashes are heard on radio, when lightning flash occurs in the sky. Reason: Electromagnetic waves having frequency of radio wave range interfere with radio waves.

• Correct answer
  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.

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