Making A Question Based Game, How to Ask Randomly

Just working with arrays & GUI using Javascript and wondering what is the best approach to asking random questions from a bank of questions in an array?

Currently using the following method to ask questions when reaching a point but it is obviously rather static i.e. correct answer button in fixed place every time.

function OnGUI ()

{

 if (drawGUI == true)
 {
 
       GUI.skin = MenuSkin;

      GUI.Box (Rect (Screen.width*0.5-51, 200, 402, 22), "What is the Second Letter in the Alphabet?");     
      
      if (GUI.Button (Rect (Screen.width*0.5-51, 230, 198,20), "A")) {
      GameObject.Find("First Person Controller").GetComponent(PlayerStats).playerScore -=2;
      }
      
      if (GUI.Button (Rect (Screen.width*0.5+153, 230, 198,20), "C")) {
      GameObject.Find("First Person Controller").GetComponent(PlayerStats).playerScore -=2;
      }
      
      if (GUI.Button (Rect (Screen.width*0.5+153, 260, 198,20), "D")) 
      {
      GameObject.Find("First Person Controller").GetComponent(PlayerStats).playerScore -=2;
      }
      
      if (GUI.Button (Rect (Screen.width*0.5-51, 260, 198,20), "B")) {
      GameObject.Find("First Person Controller").GetComponent(PlayerStats).playerScore +=10;
      changeDoorState();         
      }
  }    

Any help would be greatly appreciated