Explanation: VHF Digital Selective Calling (DSC) uses Frequency Shift Keying (FSK) for its signaling. The international standard (ITU-R M.493) specifies these precise parameters for reliable communication. The two frequencies used to represent the "mark" and "space" (binary 1 and 0) are 1300 Hz and 2100 Hz, respectively. The sub-carrier frequency is the center frequency around which this shift occurs. It is calculated as the average of the two keying frequencies: (1300 Hz + 2100 Hz) / 2 = 1700 Hz. This results in a frequency shift of +/- 400 Hz from the 1700 Hz sub-carrier. Therefore, the correct frequency shift is between 1300 Hz and 2100 Hz, with a sub-carrier of 1700 Hz. The other options provide incorrect frequency ranges or sub-carrier values that do not conform to the established international standards for VHF-DSC.