Identify the incorrect statement among the following:

• A

  Viscosity of liquid always decreases with increase in temperature
• B

  Surface tension of liquid always decreases with increase in temperature
• Correct answer
  C

  Viscosity of liquid always increases in presence of impurity
• Correct answer
  D

  Surface tension of liquid always increases in presence of impurity

Hence, the correct answer is options: 'C', 'D'.