细菌在¹⁴N培养基中繁殖数代后，使细菌DNA的含氮碱基皆含有¹⁴N，然后再移入¹⁵N培养基中培养，抽取其子代的DNA经高速离心分离，图①～⑤为可能的结果，下列叙述中不正确的是（　　）

阅读朱自清的《春》，完成后面的题目。
        ①盼望着，盼望着，东风来了，春天的脚步近了。
        ②一切都像刚睡醒的样子，欣欣然张开了眼。山朗润起来了，水涨起来了，太阳的脸红起来了。
        ③小草偷偷地从土里钻出来，嫩嫩的，绿绿的。园子里，田野里，瞧去，一大片一大片满是的。坐着，躺着，打两个滚，踢几脚球，赛几趟跑，捉几回迷藏。风轻悄悄的，草软绵绵的。
④桃树、杏树、梨树，你不让我，我不让你，都开满了花赶趟儿。红的像火，粉的像霞，白的像雪。花里带着甜味儿，闭了眼，树上仿佛已经满是桃儿、杏儿、梨儿。花下成千成百的蜜蜂嗡嗡地闹着，大小的蝴蝶飞来飞去。野花遍地是：杂样儿，有名字的，没名字的，散在花丛里，像眼睛，像星星，还眨呀眨的。
        ⑤“吹面不寒杨柳风”，不错的，像母亲的手抚摸着你。风里带来些新翻的泥土的气息，混着青草味儿，还有各种花的香，都在微微润湿的空气里酝酿。鸟儿将巢安在繁花嫩叶当中，高兴起来了，呼朋引伴地卖弄清脆的喉咙，唱出宛转的曲子，跟轻风流水应和着。牛背上牧童的短笛，这时候也成天在嘹亮地响着。
        ⑥雨是最寻常的，一下就是三两天。可别恼。看，像牛毛，像花针，像细丝，密密地斜织着，人家屋顶上全笼着一层薄烟。树叶儿却绿得发亮，小草也青得逼你的眼。傍晚时候，上灯了，一点点黄晕的光，烘托出一片这安静而和平的夜。在乡下，小路上，石桥边，有撑起伞慢慢走着的人；还有地里工作的农民，披着蓑戴着笠。他们的草屋，稀稀疏疏的，在雨里静默着。
        ⑦天上风筝渐渐多了，地上孩子也多了。城里乡下，家家户户，老老小小，也赶趟儿似的，一个个都出来了。舒活舒活筋骨，抖擞抖擞精神，各做各的一份儿事去，“一年之计在于春”；刚起头儿，有的是工夫，有的是希望。
        ⑧春天像刚落地的娃娃，从头到脚都是新的，它生长着。
        ⑨春天像小姑娘，花枝招展的，笑着，走着。
        ⑩春天像健壮的青年，有铁一般的胳膊和腰脚，他领着我们上前去。

根据短文内容，从短文后的选项中选出能填入空白处的最佳选项。选项中有两项为多余选项。

    Maybe you are an ordinary student. ____ This is not necessarily so. Anyone can become a better student if he or she wants to. Here's how:

    Plan your time carefully. When planning your work, you should make a list of things that you have to do. After making this list, you should make a schedule of your time. First arrange your time for eating, sleeping, dressing, etc, then decide a good, regular time for studying. ____ A weekly schedule may not solve all your problems, but it will force you realize what is happening to your time.

    Make good use of your time in class. ____ Listening carefully in class means less work later. Taking notes will help you remember what the teacher says.

    Study regularly. When you get home from school, go over your notes, review the important points that your teacher is going to discuss the next day, read that material. ____ If you do these things regularly, the material will become more meaningful, and you will remember it longer.

    Develop a good attitude towards tests. The purpose of a test is to show what you have learned about a subject. The world won't end if you don't pass a test, so don't be over worried.

    ____ You will probably discover many others after you have tried these.

A. This will help you understand the next class.

B. You probably think you will never be a top student.

C. Don't forget to set aside enough time for entertainment.

D. No one can become a top student unless he or she works hard.

E. There are other methods that might help you with your study.

F. Take advantage of class time to listen to everything the teacher says.

G. Make full use of spare time to take note of what the teacher says in class.

将下列陈述句改成反问句

①21世纪图书馆的大门不会关闭。

②同窗五载的情谊，我们不能忘记。