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: soil is formed by weathering. 
Fact 2: Soils are formed by breakdown of rock.

A: Weathering is the breakdown of rock.
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Q: Fact 1: Antigens are molecules that the immune system recognizes as foreign to the body. 
Fact 2: An antibody binds to an antigen .

A: antibodies binds to molecules.
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Q: Fact 1: a car engine usually converts gasoline into motion and heat through combustion. 
Fact 2: An internal combustion engine burns a mixture of fuel and air.

A:
A car engine burns fuel and air to create motion.
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