The condition under which a microwave oven heats up a food item containing water molecules most efficiently is

• Correct answer
  A

  the frequency of the microwave must match the resonant frequency of the water molecules
• B

  the frequency of the microwave has no relation with natural frequency of water molecules
• C

  microwave are heat waves, so always produce heating
• D

  infrared waves produce heating in a microwave oven

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