I have imported separate audio files into multiple slides. The audio files are triggered by hotspots. Some slides all audio plays when the hotspots are clicked on, and other slides none of the audio files play when the hotspots are clicked on. The same animation format is used for all.
When dealing with multiple audio tracks, Presenter is probably not the right tool. While you can add audio to specific items in PPT, that doesn't really translate to Presenter. When an animation happens in Presenter, the slide plays so the audio for the slide should play additionally the audio you associated with the quiz answer may also play.
Now, it is also worth mentioning that for audio to play in Presenter, it needs to be added through the tools in Presenter. Embedding audio through PPT won't translate when the project is published as Flash or HTML.
Based on what you are looking to do, I'd recommend looking at Captivate, as you can add audio to individual objects as well as the slides and they can play independently of one another.
Presenter has limited functionality, and some of that is due to its need to adhere to Microsoft's rules as well as being an Adobe product. Whereas Captivate is just an Adobe product. Think of Captivate as Adobe's over engineered version of PPT.