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.

Ex Input:
Fact 1: a valley is formed by a river flowing. 
Fact 2: Examples are Napa Valley and Sonoma Valley.

Ex Output:
Napa and Sonoma were formed by a river flowing.


Ex Input:
Fact 1: using a gasoline engine requires burning gasoline. 
Fact 2: Oil and gasoline are fossil fuels.

Ex Output:
Many engines burn fossil fuels.


Ex Input:
Fact 1: eyes are used for seeing by animals by sensing light. 
Fact 2: Light waves are electromagnetic waves.

Ex Output:

eyes are used for seeing by animals by sensing electromagnetic waves.