为探究“影响电磁铁磁性强弱的因素”，小明用电池（电压一定）、滑动变阻器、数量较多的大头针、铁钉以及较长导线为主要器材，进行如图所示的简易实验．

（1）他将导线绕在铁钉上制成简易电磁铁，并巧妙地通过____ 来显示电磁铁磁性的强弱，下面的实验也用这种方法的是____ 

A、认识电压时，我们可以用水压来类比

B、用光线来描述光通过的路径

C、把敲响的音叉接触水面，看有没有溅起水花，来判断音叉有没有振动

D、用斜面小车研究阻力对物体运动的影响

（2）连接好电路，使变阻器连入电路的阻值较大，闭合开关，观察到如图甲所示的情景：接着，移动变阻器滑片，使其连入电路的阻值变小，观察到图乙所示的情景，比较图甲和乙，可知____ 图中的电流较小，从而发现，通过电磁铁的电流越____ （选填“大”或“小”）磁性越强．

Hi, everybody!
    Welcome to our newly-opened Richards Cinema Bookstore!
    Now let me introduce to you some of the new film books in our store.
Are you Chinese film fans? OK, here comes the latest 25 New Takes about Chinese films. It is a collection of 25 fresh readings of different Chinese films from the 1930s to the present. In recent years, Chinese films are very popular in the States, such as Crouching Tiger and Hidden Dragon, Hero, and Flowers of Shanghai.
    Do you like French films? Well, here is The French Cinema Book. It covers French films from the 1890s to the beginning of the 21st century. It is written for all lovers of French cinema: students and teachers, specialists and fans, and so on.
    Maybe you are Indian film fans and star-chasers. Then here is Encyclopedia (百科全书) of Indian Cinema. The book is a complete introduction to all the best Indian films. It also offers a full list of names of the famous and successful film stars in the past ten years. You know, the Indian film industry is the largest in the world after our Hollywood.
    If you like British films, we have The British Cinema Book. It is a good review of British cinema. This book contains a good many nice pictures.
    In our bookstore, you can also find books about Mexican, Japanese, Australian, German and Italian films.
Well, please help yourselves to some coffee or tea, and have a good time here!

实验室用含杂质的锌运稀硫酸反应制取氢气，取8g含杂质的锌粒于烧杯中（所含杂质不溶于水，也不与酸反应），向其中加入74.2g稀硫酸，恰好完全反应后烧杯内剩余物质的质量为82g．计算：

数据198，199，200，201，202的方差是____．

按照括号里的要求完成下列句子改写。