题目

Mr. Reynolds, my teacher, handed us a list of thoughts, and asked us to write a paper on one of those thoughts. I chose the topic I wonder why things are the way they are.I wrote down all the questions that puzzled (困扰) me about life. I realized that many of them were hard to answer, and perhaps others could not be answered at all. When I handed in my paper, I was afraid that I might fail because I did not answer the questions.The next day, Mr. Reynolds handed me the paper and asked me to read it for the class. The other students became quiet as I began to read my story:Mum, why are the ro小明用显微镜观察下列细胞，其中具有细胞壁但无叶绿体的是（ ）A．菠菜叶肉细胞B．洋葱鳞片叶内表皮C．人体口腔上皮细胞D．血涂片中的红细胞