Normal air contains approximately what percentage of oxygen?

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Multiple Choice

Normal air contains approximately what percentage of oxygen?

Explanation:
Oxygen makes up a little about one-fifth of dry air at sea level, with a precise value around 20.95% by volume. The option 20.8% matches this more closely when you round to one decimal place, which is why it’s the best choice here. The 21% choice is a common rough approximation, but 20.8% reflects the standard figure more precisely. The other two options are farther from the true fraction.

Oxygen makes up a little about one-fifth of dry air at sea level, with a precise value around 20.95% by volume. The option 20.8% matches this more closely when you round to one decimal place, which is why it’s the best choice here. The 21% choice is a common rough approximation, but 20.8% reflects the standard figure more precisely. The other two options are farther from the true fraction.

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