Which of the following is an acceptable bandwidth for digital voice or slow-scan TV transmissions made on the HF amateur bands?

On the HF amateur bands, spectrum space is highly limited and heavily utilized. Because of this, FCC rules restrict the bandwidth of digital voice and slow-scan TV (SSTV) transmissions to roughly that of a standard single-sideband (SSB) voice signal, which is 3 kHz. Transmitting with a wider bandwidth, such as 10 kHz or 20 kHz, is prohibited on HF because it would cause significant interference to adjacent stations. These wider bandwidths are reserved for VHF and higher frequencies where considerably more spectrum space is available.