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: energy is used for heating a building by a heating system. 
Fact 2: Energy used for heating is the single most commonly used form of energy worldwide.

A: Heating buildings is a very common production of energy worldwide.
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Q: Fact 1: hearing is used for sensing sound by animals. 
Fact 2: Sound waves enter the ear, and are then amplified.

A: Animals use ears to hear.
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Q: Fact 1: Most genes contain the instructions for a single protein. 
Fact 2: Genes are molecules that contain the instructions for cells to work correctly.

A:
Genes are molecules that contain a single protein.
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