function showpopA() {
document.getElementById("featureA").style.display = "block" ;
document.getElementById("featureB").style.display = "none" ;
document.getElementById("featureC").style.display = "none" ;
document.getElementById("featureD").style.display = "none" ;
document.getElementById("captionA").style.display = "block" ;
document.getElementById("captionB").style.display = "none" ;
document.getElementById("captionC").style.display = "none" ;
document.getElementById("captionD").style.display = "none" ;
}

function showpopB() {
document.getElementById("featureA").style.display = "none" ;
document.getElementById("featureB").style.display = "block" ;
document.getElementById("featureC").style.display = "none" ;
document.getElementById("featureD").style.display = "none" ;
document.getElementById("captionA").style.display = "none" ;
document.getElementById("captionB").style.display = "block" ;
document.getElementById("captionC").style.display = "none" ;
document.getElementById("captionD").style.display = "none" ;
}

function showpopC() {
document.getElementById("featureA").style.display = "none" ;
document.getElementById("featureB").style.display = "none" ;
document.getElementById("featureC").style.display = "block" ;
document.getElementById("featureD").style.display = "none" ;
document.getElementById("captionA").style.display = "none" ;
document.getElementById("captionB").style.display = "none" ;
document.getElementById("captionC").style.display = "block" ;
document.getElementById("captionD").style.display = "none" ;
}

function showpopD() {

document.getElementById("featureA").style.display = "none" ;
document.getElementById("featureB").style.display = "none" ;
document.getElementById("featureC").style.display = "none" ;
document.getElementById("featureD").style.display = "block" ;
document.getElementById("captionA").style.display = "none" ;
document.getElementById("captionB").style.display = "none" ;
document.getElementById("captionC").style.display = "none" ;
document.getElementById("captionD").style.display = "block" ;
}