如图是电源电压恒为220V的电热烘干箱的基本电路图，S是双掷开关，R₁是发热电阻，定值电阻R₂为110Ω，当S接“2”时，R₁的电功率是110W，试求：

小明统计了他家今年5月份打电话的次数及通话时间，并列出了频数分布表：

则通话时间超过15min的频率为____．

    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。

“竭泽而渔，岂不得鱼，而明年无鱼”体现了可持续发展的（　　）