Explanation: An antenna tuner, also called a transmatch or antenna matching unit (AMU), serves to present an optimal impedance match between the transceiver and the antenna system. While an antenna might be resonant at a specific frequency, its impedance often deviates from the transceiver's ideal output impedance (typically 50 ohms) when operating on other frequencies. The tuner transforms this impedance, allowing the radio to "see" a 50-ohm load, thereby enabling it to deliver maximum power to the antenna for efficient radiation. This effectively "matches the antenna to the operating frequency" from the radio's perspective, minimizing reflected power (lowering VSWR) on the feedline between the radio and the tuner. Options A and C are incorrect because minimizing carrier output or maximizing VSWR are detrimental to efficient communication; the tuner aims to do the opposite—maximize power transfer and minimize VSWR. Option B is incorrect as the tuner's function is impedance matching for the entire signal, not manipulation of sidebands.