福建省地处中国东南沿海，属于亚热带气候。森林覆盖率65.95%，继续位居全国首位，生态环境状况指数继续保持全国前列。福建全省环境质量持续保持优良，是水、大气、生态全优的省份之一。

如图所示，水平桌面上平放一叠共计54张的扑克牌，每一张的质量均为m．用一手指以竖直向下的力压第1 张牌，并以一定速度向右移动手指，确保手指与第1 张牌之间有相对滑动．设最大静摩擦力与滑动摩擦力相同，手指与第l 张牌之间的动摩擦因数为 ，牌间的动摩擦因数均为 ，第54 张牌与桌面间的动摩擦因数为 ，且有 ．则下列说法正确的是(     )

阅读短文，然后根据要求完成任务。
　  Do you carry too much on the way to school or home? Don’t worry．Try e-readers (电子阅读器) and say goodbye to your heavy schoolbag．
   An e-reader has the memory space to hold hundreds of books．So people want to (A)扔掉沉书包 and read with small, light e-readers．For example，Cushing Academy，a high school in Massachusetts，USA，replaced (替换) most of the 20，000 books in (B) its library last summer．Teachers and students will use e-readers instead．
   Most e-readers are thin and weigh less than 500g．They can download (下载) an e-book in 60 seconds．“It’s (C) so easy．You can have a lot of books right at your fingers!” said Meghan Chensusky．
   Chinese schoolchildren are also trying e-readers．At the Shanghai World Expo (世博会)，an e-schoolbag is now on show．It is a special e-reader．Students can use it to download textbooks from the school servers (服务器)．(D)It can also send and receive homework．Some Schools in Beijing and Shanghai have tried this e-schoolbag for a few years．“It’s excellent．I (E)don’t have to carry a heaw schoolbag anymore，”said Xiao Qi，15，Beijing．
   New e-readers are not just for reading．They have Wi-Fi and multimedia (无线电视和多媒体)．Parents worry that these may hurt their children’s study habits． “I think Wi-Fi is not necessary for kids，”said Zeng Wenwen，43， Beijing．

下列划线字读音全对的一项是（    ）

解释下列词语。

①察觉：

②毫不理会：