function combo1() {
  document.all.contents1.style.display="block";
  document.all.contents2.style.display="none";
  document.all.contents3.style.display="none";
  document.all.contents5.style.display="none";
}
function combo2() {
  document.all.contents1.style.display="none";
  document.all.contents2.style.display="block";
  document.all.contents3.style.display="none";
  document.all.contents5.style.display="none";
}

function combo3() {
  document.all.contents1.style.display="none";
  document.all.contents2.style.display="none";
  document.all.contents3.style.display="block";
  document.all.contents5.style.display="none";
}
function combo4() {
  document.all.contents1.style.display="none";
  document.all.contents2.style.display="none";
  document.all.contents3.style.display="none";
  document.all.contents5.style.display="none";
}
function combo5() {
  document.all.contents1.style.display="none";
  document.all.contents2.style.display="none";
  document.all.contents3.style.display="none";
  document.all.contents5.style.display="block"; 
}