（1）在AgNO₃、Mg（NO₃）₂和Cu（NO₃）₂的混合溶液中，加入一定量的铁粉充分反应，过滤，洗涤，将滤渣放入盐酸中有气泡产生，滤液中存在的阳离子是______；

（2）在天平两端的烧杯中盛有等质量，等质量分数的盐酸，天平平衡．分别向一只烧杯中加入一定质量的镁，另一只烧杯中加入一定质量的铝，充分反应后，天平仍平衡，则加入Mg和Al的质量比是______．

Apple has entered the textbook market. The tech giant introduced iBooks textbooks a couple of weeks ago when it announced its iBooks 2 platform.  They are digital books in a variety of subjects from astronomy to zoology taking in science, maths, history and geography. Apple developed its iPad-based textbooks in connection with major textbook publishers. The company offers a collection of textbooks for high school students.

It sounds like good news for pupils and students. Think of it. No more carrying heavy backpacks full of textbooks. Every textbook you require can be stored on your iPad. Of course there’s a catch. You need to own an iPad and as you know, it is not cheap. You also need to buy digital textbooks, mostly priced each at $14.99 (94.74 yuan) or less. Textbook publishing was worth $8.7 billion in the US alone last year. Will digital books take over completely in education? Is learning going to evolve into something we do on an electronic tablet computer? That remains to be seen.

1.以约30个词概括上文的主要内容。

2.以约120个词就“电子教科书能否代替传统教科书”的话题谈谈你的想法，内容包括：

（1）比较电子教科书和传统教科书各自的优势；

（2）你认为将来电子教科书能否代替传统教科书呢？为什么？

1.作文中可以使用亲身经历或虚构的故事，也可以参照阅读材料的内容，但不得直接引用原文中的句子。

2.作文中不能出现真实姓名和学校名称。

概括准确，语言规范，内容合适，语篇连贯。