Which one of the following statements is $WRONG$?

  • A
    Radio waves in the frequency range $10 \ MHz$ to $20 \ MHz$ are called sky waves.
  • B
    Radio horizon of the transmitting antenna for space wave is $d_T = \sqrt{2Rh_T}$ ($R =$ radius of earth, $h_T =$ height of transmitting antenna).
  • C
    Fiber optical communication is almost free from electrical disturbances.
  • D
    The principle of fibre optical communication is total internal reflection.

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