Which of the following can be used to enter a transceiver’s operating frequency?

To change the frequency on a modern transceiver, you typically use either a direct numeric keypad or the Variable Frequency Oscillator (VFO) tuning knob. The keypad allows for quick, exact entry, while the VFO knob is used to dial through frequencies continuously. Other options are incorrect because CTCSS and DTMF encoders generate audio tones used for repeater access or remote commands, not for setting the radio's receiving or transmitting frequency. Automatic Frequency Control (AFC) is a receiver circuit that locks onto an incoming signal, not a manual user input method.