Assertion : Machine parts are jammed in winter. Reason : The viscosity of lubricant used in machine parts increase at low temperatures.

• 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'.