Based On Picklist Value - Section/Tab Hiding:

function fun()
{
var secname=Xrm.Page.getAttribute("new_optionset").getSelectedOption().text;
if(secname=="A")
{
Xrm.Page.ui.tabs.get("Lables").sections.get("Vowel").setVisible(true);
Xrm.Page.ui.tabs.get("Lables").sections.get("Cons").setVisible(false);
}
}