point at，point to，point out
point at，point to和point out的意思都与“指”有关，但还是有一定区别。
point at习惯上表示指向离说话人较近的事物，意为“指着”，at是介词，着重于指的对象。
Don’t point at the words while you are reading. 读书时不要用手指着字。
The teacher pointed at the blackboard and said，“You must look carefully.”
老师指着黑板说：“你必须看仔细。”
poi...
