"why not do sth""why not to do sth"which is right

"why not do sth""why not to do sth"which is right why not do sth why not +do sth why not doing sth还是why not do sth还是why not to do sth why not to do sth对吗?waiting Why not doing sth.make sb.to do sth. why not后面是doing sth还是 to do sth 那个语法是why not to do Sth还是why not do Sth 是Why not to do sth还是Why not do sth? 22题,不是有why not to do sth why don't you do sth 是why bot do sth.还是why not to do sth. why not do sth ?的用法