Explanation: In single-sideband (SSB) transmission, an audio signal modulates a carrier, producing both an upper sideband (USB) and a lower sideband (LSB), along with the carrier. To create an SSB signal, the unwanted sideband and often the carrier must be removed. This is primarily accomplished by using a highly selective filter. If the objective is to eliminate the lower sideband (to transmit USB), a filter is designed with a passband that allows the upper sideband frequencies to pass through while sharply attenuating the lower sideband and any remaining carrier frequency components. Conversely, if transmitting LSB, the filter would pass the LSB and block the USB. A double-balanced mixer (DBM), mentioned in options A and C, is used to suppress the carrier in the initial modulation stage, creating a double-sideband, suppressed-carrier (DSB-SC) signal. It does not selectively eliminate one sideband over the other. Option B describes the process for creating LSB, not eliminating the LSB to achieve USB.