var pre_id;
pre_id=0;

function ToggleAnswer(id) {
  if (pre_id!=id){
  	var hquestion = document.getElementById('q'+pre_id);
	var hanswer   = document.getElementById('a'+pre_id);	

  }
  pre_id=id;
  
  var question = document.getElementById('q'+id);
  var answer   = document.getElementById('a'+id);

  if (question.className == 'hide') {
    question.className = 'show';
    answer.className   = 'show';
	hquestion.className = 'hide';
	hanswer.className   = 'hide';
  } else {
    question.className = 'hide';
    answer.className   = 'hide';
  }
}