Assertion : When a bottle of cold carbonated drink is opened, a slight fog forms around the opening. Reason : Adiabatic expansion of the gas causes lowering of temperature and condensation of water vapours.

• Correct answer
  A

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

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

  if assertion is true but reason is false
• D

  if both assertion and reason are false statements.

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