To make a random selection from a list you first have to have the list. An array makes a good list, so for each category create an array and fill each with whichever choices you intend.
To randomly pick one of the items in the list you can use the Math methods that Actionscript is supported by.
var whoList:Array = [1,2,3];
var randomWho = whoList[Math.floor(Math.random()*whoList.length)];
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