为测定一木块与木板间的动摩擦因数，同学甲设计了两种方案．

方案一：木板水平固定，通过弹簧秤水平匀速拉动木块，如图a；

方案二：木块固定，通过细线水平拉动木板，如图b．

2009年10月6日，华裔物理学家高锟因为“在光学通信领域中光的传输的开创性成就”而获得诺贝尔物理学奖。下列关于光纤通信的说法中，正确的是 （）       

    Tom is a schoolboy.He is only seven years old, but he is very busy on weekdays.One Saturday he decided to relax himself, so he went to the cinema.

    It was the first time for him to do that.He bought a ticket and then went in.But after two or three minutes he came out, bought a second ticket and went in again.After a few minutes he came out again and bought a third ticket.Two or three minutes later he came out and asked for another ticket.Then the girl in the ticket office asked him, “Why did you buy so many tickets? How many friends did you meet?” Tom answered, “No, I have no friends here.But a big boy always stops me at the door and tears(撕) my ticket.”