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: soil is formed by rocks eroding. 
Fact 2: Soils are formed by breakdown of rock.
rocks eroding causes them to breakdown.

Fact 1: pollutants have a negative impact on the environment. 
Fact 2: Environment and Health Environment and Health All living things depend on their environment.
pollutants have a negative impact on all living things.

Fact 1: sound can be used for communication by animals. 
Fact 2: Sounds are vibrations in air.

Vibrations in air can be used for communication by animals.