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: Any surface that has not been sterilized is likely to be covered with bacteria. 
Fact 2: Surfaces can be steamed cleaned and sterilized.

A: Any surface that has not been cleaned is likely to be covered with bacteria.
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Q: Fact 1: boulders are formed by glaciers melting sometimes. 
Fact 2: Glaciers are made of snow, ice and rock.

A: boulders are formed by snow, ice, and rock melting sometimes.
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Q: Fact 1: gases released during the use of fossil fuels causes global warming. 
Fact 2: Sea level rise is caused by global warming and the fastest growing source is air traffic.

A:
gases released during the use of fossil fuels causes sea level rise.
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