阅读下列材料，回答问题。

材料  到第二次工业革命时期，电力代替了蒸汽动力，使工业动力结构发生了重大改进。发电机的问世和电力的广泛应用使工业赖以发展的动力更强大、持久和稳定。

    The listening test is one of the most important parts of the English exams. Here are some tips on listening for you.

    Before you start to listen, you need to relax. Don't be nervous. And try to read the questions. These questions usually help you understand the dialogue or the passage.

    Then listen to the first sentence carefully. It usually tells you the main idea of the passage. When you're listening, try to do some thinking and take some notes(笔记), such as：

    What happened?

    When, where, and how?

    What does the speaker want to tell us?

    In this way, you may understand the passage better.

    Please remember not to think about one or two words for a long time. When you hear some words you don't know, don't spend too much time on them. Very often, you'll find out what they mean later when you go on with the listening.

⑴题完成句子；(2)～(3)题简略回答问题；(4)题找出并写出文章的主题句；(5)题将文中画线句子译成汉语。

显微镜视野中出现了一个污点，转动目镜和移动玻片标本时，这个污点都不动，它最可能在（  ）