Supposed that you have your 3 arrays of questions, so to get the question, you can do like this :
var question_01:Array = ['question 01', 'answer 01', 'answer 02', 'answer 03', 'answer 04'];
var question_02:Array = ['question 02', 'answer 01', 'answer 02', 'answer 03', 'answer 04'];
var question_03:Array = ['question 03', 'answer 01', 'answer 02', 'answer 03', 'answer 04'];
var selected_question:int = Math.ceil(Math.random() * 3); // gives : 1, 2 or 3
trace(this['question_0' + selected_question][0]); // gives : question 01, for example
You can also put your questions arrays into an array like this :
var questions:Array = [
['question 01', 'answer 011', 'answer 02', 'answer 03', 'answer 04'],
['question 02', 'answer 012', 'answer 02', 'answer 03', 'answer 04'],
['question 03', 'answer 013', 'answer 02', 'answer 03', 'answer 04']
];
selected_question = Math.floor(Math.random() * 3); // gives : 0, 1 or 2
trace(questions[selected_question][0]); // gives : question 02, for example
Hope that can help.