Cho các phản ứng sau: 

Các phản ứng đều tạo khí N₂ là: 

A. (1), (3), (4).

B. (1), (2), (5).

C. (2), (4), (6).

D. (3), (5), (6).

Enviroment is the most important thing for our life. Enviroment is the air we breath, the water we drink and is everything we need for our life. But now that most important thing for our life is being polluted and by many different ways. This pollution affects the health of living things. Air is damaged by car and lorry fumes, and power stations create acid rain which destroys entire forests and lakes. When fossil fuels i.e. oil, gas and coal are burned to provide energy for lighting, cooking etc. they form polluting gases. Not only on land but also in the sea, oils spills pollute sea water and kill marine life; chemical waste from factories and sewage works, and artificial fertilisers from farmland, pollute river water, killing wildlife and spreading disease. Everything is being caused by human’s existence. Humans create such a lot of rubbish! Each household produces about 1 tonne of rubbish every year! Most of this is taken away by dustmen and buried in enormous landfill sites or burned in incinerators - both of these actions can be dangerous for the environment.

But only we can change it and solve it. Pollution can be prevented by thing we do everyday. First we can use recycled paper to help save trees. Second try to avoid buying plastic. It's hard to recycle. One way to cut down on plastic is to refuse to use carrier bags. If we can’t avoid buying plastic bags, we should use re-use plastic bags over and over again, until they wear out. Finally we should take your old clothes to charity shops, some are sold. To protect environment we also have to save energy. Use less energy by switching off lights when rooms are not in use, not wasting water; don’t forget to switch off all electric things when they are not in use, use a bicycle or walk instead of using a car for short trips we can save energy, keep clean atmosphere and keep healthy life. Lighting accounts for 10 percent to 15 percent of the electricity bill. However, this amount can be reduced by replacing an ordinary 100-watt light bulb with an energy-saving bulb and we still trying to invent the new thing to save money as well as conserve the Earth’s resources.

Keep clean environment isn’t only all ways are mentioned before but also to protect natural resources. That is the way to conserver wild life. First we need to conserve the old forest, rainforest, build more safari and national park, and plant more trees to make place to live for wild animals. Second we need to prohibit hunters who hunt animals too many out of the law allowance.

Finally, we now know that enviroment is the most important thing for life and we know how to protect and use it scientifically. Everyday we invent and find more and more way to protect enviroment. I hope that in the future the earth will be cleaner.

Cho các chất: CH₃CHO, C₂H₅OH, H₂O. Chiều giảm dần nhiệt độ sôi của các chất là

A. H₂O, C₂H₅OH, CH₃CHO.

B. H₂O, CH₃CHO, C₂H₅OH.

C. CH₃CHO, H₂O, C₂H₅OH.

D. CH₃CHO, C₂H₅OH, H₂O

Lỗi sai là " the table tennis "

Sửa lại: Do you play table tennis?