题目

I was sleeping in my room when my bed started shaking and a loud noise was heard. I woke up and my mom was screaming my name. Next moment I was running along with my younger sister, mom and dad. Before I ran out of the door, I realized my elder sister hadn’t come out yet. So I screamed her name at the top of my voice. My mom said she had gone to her class. Then the four of us, along with many others, were running on the staircase. We lived on the seventh floor, so I thought we would not be able to make it and the building would fall before we managed to reach even the fourth floor. M7．在正方形中剪一个最大的圆，已知正方形边长为20m，圆面积为314平方厘米．