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

• A

  Microwaves are heat waves, so always produce heating

• B

  Infra -red waves produce heating in a microwave oven.

• C

  The frequency of the microwaves must match the resonant frequency of the water molecules

• D

  The frequency of the microwaves has no relation with natural frequency of water molecules