MacBook – No audio in Safe Mode

From the technical specification:

Audio

Stereo speakers with subwoofer
Omnidirectional microphone
Headphone port
Support for Apple iPhone headset with remote and microphone
Support for audio line out (digital/analog)

There is no direct "microphone in" or "line in" connector. The only way to connect a microphone is to use a splitter meant for iPhone and similar devices, like this one. You should note that the input is mono only, no stereo support.

When I asked this question, I only had one option in the audio output devices list in my audio preferences. When I went back some time later, I noticed an option called [someone's name] - Macbook Air. I accidentally clicked it, and quickly set the setting back to my headphones. This seems to have fixed the problem.