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: hydropower requires damming a river. 
Fact 2: Hydropower is a renewable resource.
Damming a river can provide a renewable resource.

Fact 1: threatening behavior causes a fight-or-flight response in animals. 
Fact 2: Any disaster that threatens humans, threatens animals as well.
fight-or-flight response happens in humans and animals.

Fact 1: a scale is used for measuring weight. 
Fact 2: All weight is in pounds.

a scale is used for measuring pounds.