instruction:
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.
question:
Fact 1: sound can be used for communication by animals. 
Fact 2: Sound occurs when a body, such as a vocal chord, vibrates, or moves back and forth.
answer:
Animals may use vocal chords to communicate.


question:
Fact 1: a valley is formed by a river flowing. 
Fact 2: Examples are Napa Valley and Sonoma Valley.
answer:
Napa and Sonoma were formed by a river flowing.


question:
Fact 1: Most aquatic organisms do not have to deal with extremes of temperature or moisture. 
Fact 2: Fish Fish are the ultimate aquatic organism.
answer:

Most fish do not have to deal with extreme temperature or moisture.