Which of the following is one of the connections required between a computer and a transceiver to operate digital modes?

In a basic digital mode setup, the computer's sound card acts as the decoder for the analog audio signals received by the radio. To accomplish this, the audio from the transceiver's speaker output (or dedicated audio out) must be routed into the computer's "line in" or "microphone" jack. Conversely, for transmitting, the computer's "line out" must go to the transceiver's microphone or auxiliary audio input. The computer generates the transmission tones and sends them out to the radio. Connecting audio lines directly to a push-to-talk (PTT) connection, as suggested by some distractors, is incorrect because PTT requires a switching signal to trigger the transmitter, not an audio stream.