题目

用电子显微镜观察到细胞结构a～d具有下列特征：a、b、c均由双层膜构成，其中a的膜上具有小孔，而b、c没有小孔，c内部含有基粒，d有一对互相垂直的结构组成，则下列叙述错误的是（）       A．                       a是细胞核                  B． b是线粒体            C．   c是内质网     D． d是中心体根据中文和英文提示，写一封意思连贯、符合逻辑、不少于60词的回信。信的开头和结尾已经给出，其词数不计入所完成的回信内，请不要写出你的校名和姓名。假如你是李华，收到你的笔友Jim的来信，信中谈到他最近沉迷于电脑游戏中，他认为这不仅有损身心健康，而且还影响学习，为此，他很苦恼。请根据这封信的内容，给Jim写一封回信，谈谈你的看法及建议。Dear Li Hua,These days I always play computer games for a long time. As a result, it is difficult for me to finish my homework on time. Also I often feel sleepy when I have lessons. I know playing computer games is bad for my study and health, but I can’t stop doing it. I’m angry with myself. What should I do? Can you give me some advice? Please write to me soon.Yours,Jim Dear Jim,Don’t be angry with yourself.                                                  Best wishes!Yours,Li Hua