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: Most mollusks have shells. 
Fact 2: Mussels are bivalve mollusks.

A: Most mussels have shells.
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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: protein is used to repair cells by the human body. 
Fact 2: DNA makes proteins, proteins build cells, and cells make up people.

A:
DNA repairs cells.
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