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。

为研究IAA（生长素）和GA（赤霉素）对植物茎伸长生长的作用，用豌豆做了一系列实验，请分析回答：

（1）分别使用不同浓度的TIBA（IAA抑制剂）和S﹣3307（GA抑制剂）处理豌豆黄化苗茎切段，测量结果如下：

①实验中____ 是对照组．

②图1中，浓度高（80和160mg•L^﹣1）的TIBA对茎切段的伸长生长有____ 作用；浓度低（10和20mg•L^﹣1）的TIBA对茎切段的伸长生长有____ 作用，这可能与TIBA本身有微弱的____ （作用）有关．

③图1、图2两组实验均出现茎切段的伸长生长受抑制现象，表明IAA和GA____ 

（2）植物体内的GA有GA₁、GA₂…等多种，已知GA₁是由GA₂₀转化而来的，转化过程如下：

有人发现，豌豆去顶后，茎杆中IAA的浓度____ ，无活性的GA₂₀向有活性的GA_l的转化也减少；由此推测IAA在____ 激素合成中起作用．

（3）为验证上述推测正确与否，做了如下实验：将豌豆的茎切段浸入含有¹⁴C的GA₂₀的培养液中，施加适宜浓度的IAA或不施加IAA，后者茎切段的代谢产物主要是含有¹⁴C的无活性GA₂₉，而前者茎切段中则是含有¹⁴C的有活性GA₁．

①他们采用了____ 技术追踪GA₂₀的转化途径．

②结果表明生长素具有____ 作用，其作用机理可能是生长素最终促进____ 酶基因的表达．

如图，在△ABC中，点D、E分别是边BC、AC的中点，过点A作AF∥BC交DE的延长线于F点，连接AD、CF．

（1）求证：四边形ADCF是平行四边形；

（2）当△ABC满足什么条件时，四边形ADCF是菱形？为什么？