雨天乘车时，小华发现小车前挡风玻璃上的刮水器随着雨的大小，刮动的速度相应地发生变化．雨停后，刮水器自动停止工作．小华查阅相关资料后，发现它的工作电路中安装有“雨水检测金属网”装置．小华想，该装置究竟在刮水器工作中起到了什么作用，于是他自制了如图甲所示的雨水检测金属网（以下简称检测网），并设计了如图乙所示模拟电路进行探究．

下图表示一项重要的生物技术，对图中物质a、b、c、d的描述，正确的是(　　)

根据短文内容，从方框中选择适当的词并用其正确形式填空，使短文通顺、意思完整，每空一词，每词限用一次。

    My name is Betty. I am twelve. I have some ____. We are middle school students. We are in Class Two, Grade Seven. This is Miss Green. She is an American teacher. She ____ us English. Her classes are very ____. We all like her.

    This is my new classroom. In the classroom you can see many ____ and chairs. A blackboard, a clock and a map ____ China are on the wall. On a desk, you can see some pencils. The red one is mine. The green one is ____.

    Look! You can see a ball under the desk. That's Kate's desk. The ball is____, too. This is my desk. You can see a ____on it.