比较和归纳是学习化学的重要方法，请你仔细观察下面三个化学变化的表达式：

C+O₂CO₂　　2H₂+O₂2H₂O　　　CO+O₂CO₂

（1）找出它们的共同点，并写出其中的三点：

①____②____ ③____

（2）找出其中一个反应与另外两个的一个不同点　____ ．

调节呼吸作用、光合作用和蒸腾作用的结构是气孔，控制气孔开闭的细胞是

根据句子意思，写出下列句子括号内所给单词的正确形式。
The children often get ____ (noise) in the classroom after class .
Sometimes he spends his weekend____ (fish).
Several____ (foreign)came to visit our school last week.
I think the red skirt looks as ____ (good)as the green one .
John just got his____ (driver) license.
Look!Mrs Li is there. Let's go and say hello to____ (she)?
My mother often____ (enjoy) the TV plays in the evening.
Talking loudly in a library is very____ (polite).
B.根据句子意思及所给的首字母或汉语提示，写出该句子中所缺的单词。
Li Na is a famous tennis p____ .
We can’t l____ to music when the teacher is talking in class.
The children had a____  been asleep when I got home .
Mr Li is s____ with his students and makes them work hard.
Zhou Gu was____ （采访）by the local  newspaper.
There are ____ (五十二)weeks in a year.
The doctor gave him some medicine for his serious____ (疾病)。

一位心理学家说过：“一个人如果没有任何阻碍，不经受任何挫折，将会永远保持其满足和平庸状态，将会变得愚蠢又糊涂。”对此，理解正确的是（    ）