题目

下列对实验的相关叙述，不正确的是（    ） A．内质网是细胞中膜面积最大的细胞器，但在普通光学显微镜下不能看到内质网、核糖体等结构 B．分泌蛋白合成、分泌过程的实验和人、鼠细胞融合实验均使用放射性同位素标记法 C．视野中观察到植物细胞原生质层与细胞壁处于分离状态据此不能判断该细胞正在失水还是吸水 D．伞藻的嫁接和核移植试验说明细胞核是遗传的控制中心9．Dear Merry，Recently，I have trouble with my study． In school I can't listen to teachers carefully because I always feel tired and sleepy．I don't spend time with friends after class either because I think it's a waste of time．I even miss writing some answers in the test． At home，I can't get my homework done every night．My parents don't let me stay up．So I have to get up early the next morning to finish it．Lately，I even get a bad headache． How can I solve these problems？Yours，LiuYa Dear Liu Ya，When you have trouble listening to teachers carefully in class，you can ask your teachers or deskmate to remind you often．Then spending time talking about many different things with friends can make you happy．It's not a waste of time．As for homework，when it's hard to get finished，one thing you can try is setting goals for yourself．Ask your parents to help you．You must take a break，especially if you don't feel well．You might be surprised but a short break can help you get more done!Lastly，if you don't worry and have enough sleep，your headache will leave you． Yours，Merry 81．Liu Ya wrote the letter to Merry in order toA．A．ask for helpB．express worriesC．share her experience82．Liu Ya doesn't want to stay with friends after class becauseB．A．she needs to sleep B．she thinks it's a waste of time C．she has trouble with her classmates83．Merry thinksA．A．taking a break is necessaryB．being with parents is helpfulC．setting goals by parents is important84．According to the underlined part，what might Liu Ya's teacher say？A．Sleep for a minute．B．Listen carefully．C．Stop talking．85．From Liu Ya's letter，we can find that she is tooC．A．passive B．proud C．stressed．