A: What's your name?
B: Thank you.
将矩形纸片ABCD按如图所示的方式折叠．恰好得到菱形AECF．若AD=3，则菱形AECF的面积为（ ）
cook, on, do, live, busy, read, play, about, clean, weekend
Hello! My name is Zhang Ming. I ____ in Qingdao. I am a student. Do you want to know about my ____? I'm very happy ____the weekend. I can ____many things(事情). Usually I do my homework and ____books. Sometimes I ____the rooms and ____dinner with my mum. I often watch TV and ____ pingpong with my father. I'm ____at home. This is my weekend. What ____your weekend?
李强是七年级学生，课外主要活动场所是学校附近的网吧，花大量时间玩网络游戏，影响了学习，还经常采用撒谎、变卖家中物品等形式弄钱上网。
阅读材料，请回答：
下列结构中，洋葱鳞片叶内表皮细胞具有的，而人体细胞中没有的是（ ）
