Explanation: A receiving antenna converts the electromagnetic field of a radio wave into an electrical voltage. The strength of this induced voltage at the antenna's terminals is directly dependent on the strength of the electromagnetic field passing through it. Therefore, the voltage is always proportional to the received field strength; a stronger signal field results in a higher induced voltage. Options A and B relate to the phase relationship between voltage and current *within* the antenna or at its feedpoint, which depends on the antenna's impedance and resonance at the operating frequency. These are internal characteristics, not the fundamental source of the induced voltage. Option C, SWR, primarily describes the impedance match between the transmission line and the antenna, affecting power transfer efficiency on both transmit and receive, but not the initial voltage induced by the incoming wave.