function checkChoice(field, i) {          // "ALL" checked
if (i == 0) {                             // Everything else unchecked
	if (field[0].checked == true) {
		for (i = 1; i < field.length; i++)
			field[i].checked = false;
	}
}
else if (i == 1) {
	field[0].checked = false;            // First 1st-level checked
	field[1].checked == true;            // ALL unchecked  
   }
else if (i == 2) {
	field[0].checked = false;            // Second 1st-level checked 
	field[2].checked == true;            // ALL unchecked 
   }
else if (i == 3) {
	field[0].checked = false;            // Third 1st-level checked
	field[3].checked == true;            // ALL unchecked 
   }
else if (i == 4) {
	field[0].checked = false;            // Fourth 1st-level checked 
	field[4].checked == true;            // ALL unchecked 
   }
}