完形填空。

    Jack is my classmate. He is my good friend. He is 1 American boy. He is from 2. He is short. He has a round face and    3 big brown eyes. His 4 is not black. It is blond (金黄色的). Tom likes English. He can speak a little Chinese, too. He goes to school 5 foot.

    We usually 6 our homework at school. We clean our classroom 7 every Friday. Usually, Tom 8 the blackboard and I sweep the floor. Our favourite sport is basketball. Sometimes we 9 in the playground. We 10 at 4.30. We both like our teachers and classmates.

情感与情绪是相辅相成的，互相影响的，下列对于情感与情绪二者之间的关系认识正确的是（    ）

①情感与情绪紧密相关              ②我们对某些人或事物的情绪随着时间的推移就可能产生某种情感

③情感与情绪是有区别的          ④情感与情绪的表达方式是一样的

（Ⅰ）求展开式中含 $\frac{1}{x}$ 项的系数

（Ⅱ）设（2x﹣ $\frac{1}{\sqrt{x}}$ ）⁵的展开式中前三项的二项式系数之和为M，（1+ax）⁶的展开式中各项系数之和为N，若4M=N，求实数a的值．

如图，△ABC是一块锐角三角形的材料，边BC=120mm，高AD=80mm，要把它加工成正方形零件，使正方形的一边在BC上，其余两个顶点分别在AB、AC上，这个正方形零件的边长是多少mm．