STOP AUDIO FOR CLICKBOXES

You need to use Play Audio in that case. Typical for audio clips started that way, is that they are automatically stopped when you start another clip with the same action Play Audio. There is no need to use Stop Triggered Audio, which also applies to audio started with Play audio command, but that is only necessary if you want to sop an audio clip independently.

I would recommend to have a shared action used for the click boxes. You didin't tell how you show the image, and I cannot see that on the screenshot: are they states in a multistate object or do you use a group with images and show one out of that group?

Adding to the images show or go to state command, you'll just have to add Play Audio. The audio will stop when another click box is clicked. 

You can find more info here:

https://elearning.adobe.com/2018/06/pausing-timeline-audio-clips/

It depends on how you are triggering the audio to play.  Are you using the click boxes to play an audio clip by triggering the Play Audio action?  If so, then you can use the Stop Triggered Audio action to stop such audio. 

But since you want any audio triggered by other click boxes to stop first this means that you would need to trigger the Stop Triggered Audio action BEFORE then triggering the Play Audio action for the click box that just got clicked.  This then means you really need to trigger multiple actions from a single click event. 

The simplest way to do this is to create a separate Advanced Action for each Click Box.  There will be two action lines.  The first line is the Stop Triggered Audio action (to stop any audio currently playing) and then the second line is the Play Audio action to play the audio corresponsing to the Click Box now being clicked. 

If you had many such Click Boxes to set up I would suggest using Shared Actions but since you only have a few Click Boxes, I would say it's not worth worring about that.