Please: need help on a hit test for class project

function createPig (i){
mov = “clip”+i;
_root.attachMovie(“myMC”, mov, i);
_root[mov]._x = -20;
_root[mov]._y = Math.random()*250;
_root[mov].speed = Math.random()*5+5;
_root[mov].onEnterFrame = fly;
}
function fly(){
this._x+=this.speed;
if(this._x > Stage.width){
this.unloadMovie();
_root.num++;
_root.createPig(_root.num);
}
}
_root.maxNum = 7;
for(_root.num=1; _root.num<_root.maxNum; _root.num++){
createPig(_root.num);
}

what would be the hittest for the pig for this duplicate/random for this mc. I am using a crosshair to hit the pigs. I am new at actionscript. Thank you for anones help