茂密的树林中，不是人们清晨锻炼的理想场所，主要原因是（ ）
A．氧气含量偏低
B．细菌含量偏少
C．尘埃被吸附在植物上
D．会打扰动物的休息
植物的光合作用是在叶绿体里利用光能把二氧化碳和水合成有机物，释放氧气，同时把光能转变成化学能储存在合成的有机物中的过程；而呼吸作用指的是细胞内有机物在氧的参与下被分解成二氧化碳和水，同时释放能量的过程．它与光合作用的区别与联系为：
| 区别 | 联系 | |||||
| 场所 | 原料 | 条件 | 产物 | 能量 | ||
| 光合作用 | 叶绿体 | 二氧化碳、水 | 光 | 有机物、氧气 | 储存能量 | 相互对立 相互依存 |
| 呼吸作用 | 所有的活细胞 | 有机物、氧气 | 有无光皆可 | 二氧化碳、水 | 释放能量 | |
故选：A
Are your table manners much better when you are eating at a friend’s home or in a restaurant than they are at your own home? Probably so, __1__ you are aware that people judge you by your table manners. You take special pains when you are eating __2__. Have you ever stopped to realize how much less self-conscious you would be on such occasions if __3__ table manners had become a habit for you? You can make them a habit by __4__ good table manners at home. Good manners at mealtimes help you and those around you to feel __5__. This is true at home as much as it is true in someone else’s home or in a restaurant. Good __6__ make meals more enjoyable for everyone at the table. By this time you probably know quite well what good table manners are. You __7__ that keeping your arms on the table, talking with your __8__ full, and wolfing down your food are not considered good manners. You know also that if you are mannerly, you say “Please” and “Thank you” and ask for things to be passed to you. Have you ever thought of a pleasant attitude as being __9__ to good table manners? Not only are pleasant mealtimes enjoyable, but they aid digestion. The dinner table is a __10__ for enjoyable conversation. It should never become a battleground. You are definitely growing in social maturity (成熟) when you try to be an agreeable table companion.
|