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 Q]: Fact 1: Gene flow occurs when individuals move into or out of a population. 
Fact 2: Geographic subdivision decreases gene flow.
[EX A]: Geographic subdivision decreases how fast individuals move into or out of a population.

[EX Q]: Fact 1: fluoride decreases tooth decay. 
Fact 2: Humans get most of their fluoride in drinking water.
[EX A]: Drinking water decreases tooth decay.

[EX Q]: Fact 1: Most protists have motility. 
Fact 2: Protists are the simplest of eukaryotes.
[EX A]:
The simplest eukaryotes have motility.