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: rain causes erosion. 
Fact 2: Erosion is the breaking apart and moving of rocks and soil.

A: Rain causes the breaking apart and moving of rocks and soil.
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Q: Fact 1: acid rain has a negative impact on water quality. 
Fact 2: Acid rain is harmful rain.

A: some rain is harmful.
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Q: Fact 1: Roundworms may be free-living or parasitic. 
Fact 2: Dogs remain susceptible to reinfection with hookworms and roundworms.

A:
Dogs remain susceptible to free-living or parasitic species.
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