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.

Fact 1: the type of material through which sound passes changes the speed at which sound travels. 
Fact 2: Sounds are made by vibrating objects.
The type of material through which a vibration passes changes the speed at which it travels.

Fact 1: Fungi are the only organisms that can decompose wood. 
Fact 2: All wood is either pine or oak.
fungi are the only organisms that can decompose pine trees.

Fact 1: wind is used for producing electricity. 
Fact 2: Wind is air in motion.

air in motion is used for producing electricity.