24. For a classical electromagnetic plane wave travelling in a vacuum, which of the following statements is true? (A) The magnetic and electric fields are perpendicular to each other, and there is a phase difference of π/2 between them. (B) The average power delivered by the EM wave increases with the frequency of the EM wave. (C) The traveling direction of the EM wave can be in either the direction of o are the direction of the electric field and the magnetic field, respectively. (D) The power of the EM wave decays as it propagates away from its source. (E) None of the above.