设f：x→ax-1为从集合A到B的映射，若f（2）=3，则f（3）=______

请根据下面短文回答第11～15题：
Reading for pleasure is the easiest way to become a better reader in English. It is also the most important way.
Some students say they don’t want to read for pleasure. They say they want to use their time to learn the rules of the language and new words. They say that pleasure reading is too easy.
Many experts(专家)say pleasure reading is very important for learning English. Dr. Stephen Krashen, a famous expert on learning languages, says that pleasure reading helps you learn many important things about English. Students learn more grammar and more words when they read for pleasure. They also learn more about good writing.
Dr. Krashen tells us that pleasure reading helps each student in a different way. Each student needs to learn something different. Pleasure reading makes it possible for each student to learn what he or she needs.
Reading for pleasure is not the same as studying. When you read for pleasure, you choose your own books, and you don’t have to remember everything. There are no tests on your pleasure reading books. Pleasure reading will help you:
—learn how English speakers use English
—read faster in English
—find examples of good writing in English
—learn new words
—learn about the cultures(文化)of English speakers

When you read for pleasure, ______.
[A] you must read very fast
[B] you can read your favorite books
[C] you must remember many new words

企业出售一项无形资产，摊余价值650万元，相关减值准备80万元，出售所得价款为165万元。为此该企业当期的损失为（）万元。

A．325

B．405

C．485

D．570

操作系统是管理计算机软硬件资源、控制程序运行、为应用软件提供支持和改善人机界面的一种系统软件。下面是有关操作系统的一些叙述：
Ⅰ．操作系统与计算机硬件无关，任何计算机均可安装任何操作系统
Ⅱ．任何一台计算机只能安装一种操作系统
Ⅲ．目前所有适用于PC机的操作系统，都是微软公司的产品
Ⅳ．Windows操作系统只能安装在C盘中
上面叙述中错误的是

A) 仅有Ⅰ
B) 仅有Ⅰ和Ⅱ
C) 仅有Ⅰ、Ⅱ和Ⅲ
D) Ⅰ、Ⅱ、Ⅲ和Ⅳ

简述YB25/YB45包装机控制面板上颜色滚动按钮的作用及使用方法。

盐分测试主要是测量金属表面的（）离子