酶是活细胞内产生的具有高度专一性和催化效率的蛋白质，又称为生_爱下问搜题

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问题单项选择题

酶是活细胞内产生的具有高度专一性和催化效率的蛋白质，又称为生物催化剂。生物体在新陈代谢过程中，几乎所有的化学反应都是在酶的催化下进行的。下列过程需要酶参与的是

A．氧气进入血液

B．光合作用吸收CO2

C．细胞质壁分离

D．叶绿体吸收光能

答案

参考答案：C

解析：【解析】考查百科知识。选C。

完形填空

One afternoon, many years ago, I went to pick up my mother from work. I got there a little early so I   1  the car by the roadside and waited for her.
As I looked   2  the car window, there was a small park where I saw a little boy, around two years old,   3  freely on the grass as his mother watched from a short   4 . The boy had a big smile on his face   5  he had just been set free from some sort of   6 . The boy would then fall to the grass,   7 , and without hesitation or without looking back at his mother, run as fast as he could again, still with a   8  on his face.
Kids, when they fall down, don't view their falling down as failure, but   9 , they treat it as a learning experience. They try and try again until they   10 . While I was touched by the boy's persistence, I was   11  touched by the manner in which he ran. With each attempt, he looked so   12  and so natural — no signs of fear, nervousness, or of being discouraged. His only   13  was to run freely and to do it as effectively as he could. He was just being a   14  — just being himself—being completely in the moment. He was not looking for   15  or was not worrying about whether   16  was watching. He didn't seem to be bothered by the fact that maybe someone would see him   17  and that it would be   18  if he did fall. No, all that   19  to him was to accomplish the task, to feel the experience of running fully and freely. I learned a lot from that   20  and experience, and have successfully brought that lesson with me in my many pursuits（追求) in life.

A．embarrassing

B．disappointing

C．frightening

B．contributed

B．observation

问答题简答题

什么是流转税？主要包括哪些具体税种？