function showAnswer(num){
   var l_name = "a" + num;
	if (document.layers){
		var current = (document.layers[l_name].display == 'block') ? 'none' : 'block';
		document.layers[l_name].display = current;
	}
	else if (document.all){
		current = (document.all[l_name].style.display == 'block') ? 'none' : 'block';
		document.all[l_name].style.display = current;
	}
	else if (document.getElementById){
		current = (document.getElementById(l_name).style.display == 'block') ? 'none' : 'block';
		document.getElementById(l_name).style.display = current;
	}
}