The higher up you go, it gets harder to breathe because air is less dense which means that there are molecules of oxygen to breathe into our lungs.

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Less is the word to ur question

The answer should be fewer based on the question. The oxygen molecules in the air are spread more thinly and therefore you take in less oxygen molecules per breath. Hope this helps!

There is no reason to think the results are biased or not conducted properly but you should not assume the results are correct just because they were done in a laboratory so the answer would be c. it is likely to be reliable because the results support the conclusion presented.

The think of process to make something successful