Two traits that represent a sustainable society is an emphasis on egalitarianism - where there would be a tendency to strive towards a society of equals. Another would be an emphasis on using renewable energy.
On the other hand, an unsustainable society would have an emphasis on using fossil fuels due to being cheaper and having an ever-increasing productions of goods, not considering how taxing this might be on the planet.
C. Because they contain water ammonia, and methane
Photosynthesis allows plants, algae and certain bacteria to turn sunlight into chemical energy. The amazing feat is achieved because sunlight can fuel a reaction between water and carbon dioxide that, in turn, produces carbohydrates (simple sugars) and oxygen.
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Absorbing CO2 into the blood is a part of the respiratory system!