You can place the second question and it's options wrapped inside a Subform and mark the Subform Presence as Hidden.
In the Exit event of the Dropdown you can check for the value and set the above Subform's presence property to Visible.
if(DropDownList1.rawValue == "Yes"){
Subform1.presence = "visible";
}
else{
Subform1.presence = "hidden";
}
Thanks
Srini