Clear elements help

Question

What would I write in the script below to hide statements that have been dragged to the target box but are not the correct answer? Right onw I have nothing but if you drag everything but the right statemnt and then drag the right statement to the target box, you proceed to the next frame but the incorrect statements are still there.
stop();
next_btn.visible = false;
spots1a1.buttonMode = true;
spots1a2.buttonMode = true;
spots1a3.buttonMode = true;
spots1a4.buttonMode = true;
spots1a5.buttonMode = true;
spots1a1.addEventListener(MouseEvent.MOUSE_DOWN, pickUp2);
spots1a1.addEventListener(MouseEvent.MOUSE_UP, dropIt2);
spots1a2.addEventListener(MouseEvent.MOUSE_DOWN, pickUp2);
spots1a2.addEventListener(MouseEvent.MOUSE_UP, dropIt2);
spots1a3.addEventListener(MouseEvent.MOUSE_DOWN, pickUp2);
spots1a3.addEventListener(MouseEvent.MOUSE_UP, dropIt2);
spots1a4.addEventListener(MouseEvent.MOUSE_DOWN, pickUp2);
spots1a4.addEventListener(MouseEvent.MOUSE_UP, dropIt2);
spots1a5.addEventListener(MouseEvent.MOUSE_DOWN, pickUp2);
spots1a5.addEventListener(MouseEvent.MOUSE_UP, dropIt2);
function pickUp2(event:MouseEvent):void {
    event.target.startDrag(true);
    answerlabel.text = "";
    event.target.parent.addChild(event.target);
    startX = event.target.x;
    startY = event.target.y;
function dropIt2(event:MouseEvent):void {
    event.target.stopDrag();
    var myTargetName2:String = "target" + event.target.name;
    var myTarget2:DisplayObject = getChildByName(myTargetName2);
    if (event.target.dropTarget != null && event.target.dropTarget.parent == myTarget2){
        answerlabel.text = "Good Job!";
        event.target.removeEventListener(MouseEvent.MOUSE_DOWN, pickUp2);
        event.target.removeEventListener(MouseEvent.MOUSE_UP, dropIt2);
        event.target.buttonMode = false;
        event.target.x = myTarget2.x;
        event.target.y = myTarget2.y;
        next_btn.visible = true;
    } else {
        answerlabel.text = "Try Again!";
        event.target.x = startX;
        event.target.y = startY;
          import flash.events.MouseEvent;
          next_btn.addEventListener(MouseEvent.CLICK, powerClick28);
          function powerClick28(Event:MouseEvent):void {
          gotoAndPlay(1009);
          spots1a4.visible = false;

Answer 1

You have the first half of that conditional which does the only testing for the object...
  if (event.target.dropTarget != null && event.target.dropTarget.parent == myTarget6){
So if you drag and drop something and it doesn't pass the tests in that line, it falls into the else condition, wherein it is turned invisible.  So you will need to add some conditions for turning it invisible only if... what?  It may require testing against every target to determine that the object was dropped on a target, or you may be satisified that it was not a null target that got hit.  You'll have to reason out your criteria for what circumstances turn it invisible and implement them in another conditional....
else {
        answerlabel5.text = "Try Again!";
        event.target.x = startX;
        event.target.y = startY;
        if(???){
            event.target.visible = false;