Combine the given two facts to write a concluding fact. Note that there should be some parts of the first and second facts that are not mentioned in this conclusion fact. Your combined fact should be the result of a chain between the two facts. Chains form when two facts connect together to produce a concluding fact. An example of a chain is: "pesticides cause pollution" (fact1) + "pollution can harm animals" (fact2) → "pesticides can harm animals" (conclusion fact). Parts of the concluding fact overlap with the first and the second fact. To construct such a  concluding fact, a useful way is to borrow the subject from one fact and the ending conclusions from another fact.

Q: Fact 1: Mammals generate heat mainly by keeping their metabolic rate high. 
Fact 2: Humans use food to generate body heat.

A: food keeps mammals' metabolic rates high.
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Q: Fact 1: Plants release oxygen during the day but not during the night. 
Fact 2: Oxygen fatigue is a shortage of oxygen reaching the brain.

A: Plants can reduce fatigue during the daytime.
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Q: Fact 1: Cells cannot survive without oxygen. 
Fact 2: Cells are the units of function in living things.

A:
living things cannot survive without oxygen.
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