I was only nine years old when I learnt how to use a computer．My mother is my first teacher．I know how to type，how to copy a file，and how to visit a website on the Internet．One day，mom was not at home．I turned on the computer and began to learn how to chat on net．The first one I met there was a boy called Tom．He greeted me politely．When he knew that I was only a 9-year-old girl and almost knew nothing about chatting on net，he started showing me how to use the chatting tools，how to download，and how to send e-mails．I learnt a lot from him．

结合本班实际，画出班级的简易平面图形，找出其中的垂线和平行线．