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: a flashlight requires a source of electricity to produce light. 
Fact 2: Flashlights and remote controlled cars get their energy from batteries.
cars use electricity.

Fact 1: erosion causes a river to become deeper and wider. 
Fact 2: Erosion alters the constituents carried by water.
Deeper and wider rivers alter the constituents carried by water.

Fact 1: Some viruses can cause cancer. 
Fact 2: Eventually the cancer kills.

some viruses can kill.