The best answer is a, if there is a phase shift between current and voltage, there will be times that the voltage and current are of opposite polarities, resulting in a negative power flow.
2. Why is it important to measure and control a transmitter's power?
a. To optimise spectral and physical space. b. Receivers in proximity to two transmitters could receive the wrong signal. c. Transmitters may have safety or regulatory limits places upon their output power. d. Too much power can drive an output amplifier into an unwanted condition, such as the nonlinear range. e. None of the above. f. All of the above