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: gills are used for breathing water by aquatic animals. 
Fact 2: Fish are backboned aquatic animals.

A: fish use gills for breathing water.
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Q: Fact 1: Complex chemistry is needed to carry out all the functions of life. 
Fact 2: Steroids are complex proteins needed to control the bodies chemistry.

A: Steroids are needed to control life functions.
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Q: Fact 1: Neurons transmit nerve impulses to other cells. 
Fact 2: Local anesthetics block nerve impulses.

A:
anesthetics block neuron transmissions.
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