看图，读一读，将字母的序号写在横线上。

A. In winter, it is cold. The ugly duckling has no home. He is very sad.

B. Uncle Lin has a garden. There are many plants in it. He waters them every day.

C. We are three little pigs. We are clever. We are not afraid of the big bad wolf.

D. Mother Duck has some eggs. She sits on the eggs.

①写出带有“七、八”的四字词。如：横七竖八

____    ____    ____    ____

②写出带有“百、千”的四字词。如：成百上千

____    ____    ____    ____

某网店经营的一红消费品的进价为每件12元，周销售量p（件）与销售价格x（元）的关系，如图中折线所示，每周各项开支合计为20元．

（1）写出周销售量p（件）与销售价格x（元）元的函数关系式；

（2）写出利润周利润y（元）与销售价格x（元）的函数关系式；

（3）当该消费品销售价格为多少元时，周利润最大？并求出最大周利润．

某22肽被水解成1个4肽，2个3肽，2个6肽，则这些短肽的氨基总数最小值及肽键总数依次是（）

病毒与细菌最明显的区别是（    ）