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问题 填空题

随着汽油、柴油的涨价，不少出租车都改用天然气作燃料，由于天然气的价格比汽油、柴油便宜，可大大降低成本．天然气的主要成分是______（写化学式），在空气中燃烧的化学方程式为______．与汽油、柴油相比，汽车改用天然气作燃料，有何优点？______、______．

答案

天然气的主要成分是甲烷．甲烷燃烧生成二氧化碳和水，化学方程式为：CH4+2O2

 点燃 
.
 
CO2+2H2O；天然气代替汽油、柴油作为汽车燃料的优点很多，如燃烧充分，热值高、污染小等．

故答案为：CH4；CH4+2O2

 点燃 
.
 
CO2+2H2O；热值高；污染小；

单项选择题 案例分析题

女性，10岁。皮肤突然出现瘀点，瘀斑，大小不等，斑色鲜红，伴鼻衄，便血，血色鲜红，并见发热。口渴心烦，腹痛呕吐，舌质红，脉细数有力。

此时应采取的治疗原则为（）

A.活血化瘀止血

B.清热凉血止血

C.疏风清热解毒

D.养阴清热凉血

E.健脾益气摄血
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问答题

Dear friends,
Water is essential for human health and well being. Water also helps to reduce poverty. Without water, there would be no life on this planet. Although water covers about two-thirds of the Earth’s surface, only 2.5% of the world’s water is drinkable.
Many millions of people around the world face water shortages. Many millions of children die every year from water-borne diseases. And drought regularly afflicts some of the world’s poorest countries. The world needs to respond much better. We need to increase water efficiency, especially in agriculture. We need to free women and girls from the daily chore of carrying water, often over great distances. We must involve them in decision-making on water management.
We need to make sanitation a priority. This is where progress is needed most. And we must show that water resources need not be a source of conflict. Instead, they can call for cooperation. Significant gains have been made. But a major effort is still required. That is why this year marks the beginning of the "Water for Life" Decade. Our goal is to meet the internationally agreed targets for water and sanitation by 2015, and to build the foundation for further progress in the years beyond.
This is an urgent matter of human development, and human dignity. Together, we can provide safe, clean water to all the world’ s people. The world’s water resources are our lifeline for survival, and for sustainable development in the 21st century. Together, we must manage them better.
Thank you.
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