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: soil is formed by weathering. 
Fact 2: Soils are formed by breakdown of rock.
[A]: Weathering is the breakdown of rock.


[Q]: Fact 1: using a gasoline engine requires burning gasoline. 
Fact 2: Oil and gasoline are fossil fuels.
[A]: Many engines burn fossil fuels.


[Q]: Fact 1: Playing is one way mammals and other animals learn how to behave. 
Fact 2: Dolphins and whales are mammals.
[A]:
playing is one way dolphins learn how to behave.