如图是小明家的一个电饭锅插座，他发现插头松动后，在使用电饭锅做饭时插头发热，并且将插座烧成了如图所示的样子，请你帮他分析产生这个现象的原因是什么？

大鼠的毛色由独立遗传的两对等位基因控制。用黄色大鼠与黑色大鼠进行杂交实验，结果如图。据图判断，下列叙述正确的是（    ）

下列关于我国地理位置优越性的叙述中，不正确的是（    ）

A

    Most Americans start to school at the age of five when they enter kindergarten(幼儿园). Children do not really study at this time. They only attend for half the day and learn what school is like. Children attend elementary school for the next six years. They learn to read and write and work with numbers. They also study the world and its people. After they leave elementary school, children go to junior high school for three years and senior high school for another three years. This is called secondary education. In some places, the children go to elementary school for eight years and high school for four. In all, elementary and secondary education together take twelve years to complete excluding （不包括）kindergarten.

根据短文，选择最恰当的选项。