function showAnswer(strStub, numSelectedQuestion, numQuestions){
  if (document.getElementById(strStub + numSelectedQuestion).style.visibility != 'visible'){
    for (numQuestion=1; numQuestion <= numQuestions; numQuestion++){
      document.getElementById(strStub + numQuestion).style.visibility = 'hidden';
      document.getElementById(strStub + numQuestion).style.display    = 'none';
    }
    document.getElementById(strStub + numSelectedQuestion).style.visibility = 'visible';
    document.getElementById(strStub + numSelectedQuestion).style.display    = 'inline';    
  }
}