Between Articulate Support (thank you!) and my boss, we figured out how to make this work.
You need to place the audio on the base layer with a trigger calling it to play when the option was clicked. What I didn't know, is when you do that, the audio file visually changes, and it doesn't play within the timeline. Instead of seeing the sound waves, you have an outline of the sound icon like this, and it jumps to the beginning of the timeline. This happens when the trigger is attached to the file.
Then to make sure the sound files never overlapped, I had to add Stop Media, which changes to Stop Audio for the other options in the event the learner clicks another before it finishes playing.
I also needed to do the same thing for the checkboxes to prevent overlapping sound if they were clicked.
When the checkboxes were clicked, they opened a layer. To keep the layers from overlapping in their sound, I selected them all and chose pause base layer, which stops them from interfering with each other. I suspect this is redundant as I'm typing this out, but I also added a stop audio set of triggers on each layer. I think doing it at the checkmark likely did this.
PHEW! That "great idea" was a lot of work. But I appreciate Walt, Joe and Support's help getting to this point.
