在平面直角坐标系中，将线段OA绕原点O逆时针旋转90°，记点A（﹣1，$\sqrt{3}$）的对应点为A₁，则A₁的坐标为（　　）

若复数z满足z=1﹣$\frac{1}{i}$（i为虚数单位），则复数z的模为（　　）

一棵树和一头牛的结构和功能的基本单位是（  ）

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.