Explanation: J2B SITOR (NBDP) is a narrow-band digital mode, similar to RTTY, that uses frequency-shift keying (FSK) to transmit data. Standard SITOR uses a 170 Hz shift between its mark and space frequencies. To contain this signal effectively and provide some guard band for spectral purity, the assigned bandwidth needs to be slightly wider than the 170 Hz shift. A 300 Hz assigned bandwidth adequately encompasses the 170 Hz FSK signal, preventing splatter into adjacent frequencies. Channel spacing dictates how far apart adjacent channels must be to avoid mutual interference. For narrow-band digital modes like SITOR, a 500 Hz channel spacing is typical, providing sufficient separation and allowing for stable communication without adjacent channel bleed-over. Options A and B describe bandwidths and spacings suitable for voice (SSB) transmissions (e.g., 3 kHz), which are far too wide for narrow-band SITOR. Option C lists 170 Hz, which is the FSK *shift* but not the overall *assigned bandwidth* which must be wider. Therefore, 300 Hz assigned bandwidth and 500 Hz channel spacing are appropriate for J2B SITOR.