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: the emission of sulfur dioxide causes acid rain. 
Fact 2: Sulfur in the coal becomes sulfur dioxide when burned.

A: Burning coal causes acid rain.
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Q: Fact 1: nerves can be used to feel heat and pressure on the skin. 
Fact 2: There are two types of nerves in the body that can "feel" pain.

A: Heat and pressure on skin can cause feelings of pain.
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Q: Fact 1: skin is used for protecting the body from harmful substances. 
Fact 2: Contamination is the unintended presence of harmful substances or microorganisms in food.

A:
The skin is used for protecting the body from contamination.
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