阅读下列短文，然后从A、B、C、D四个选项中选出最佳答案。
(D)
Readers (《朗读者》) is a popular TV show in China. It invites (邀请) people to read aloud (大声地) on the stage (舞台). The show also tells moving (感人的) stories behind those people. They can read everything, like poems (诗), books, and letters.
Many people are fans of the show. They begin (开始) to enjoy reading aloud at home.
Now, the show gives people a place to read. It is a reading pavilion (朗读亭). It showed up in cities like Shanghai, Hangzhou and Xi'an. Let's have a look!
The pavilion is not very big. Only (只有) one person can come into it each (每一) time. There is a microphone (麦克风) in it and it records (记录) people's voices.
Everyone can read for three minutes in it. You can read anything you like. The show will pick (挑选) some of the readers and invite them to read on TV.
Lots of people come to the pavilion to read. Yu Duohan is an 11-year-old girl from Shanghai. She read the story Take a Snail for a Walk (《牵一只蜗牛去散步》). "I love reading aloud," she said. "It makes the story become more beautiful."
The pavilion will also come to other cities across the country (国家). You can read your favorite stories in the pavilion soon.
度为v，经过c点时的速度为3v，则ab段与ac段位移之比为( )