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: living underground can be used for hiding from predators. 
Fact 2: Predator and prey play a deadly game of hide and seek.
Living underground can be used to avoid playing a deadly game of hide and seek.

Fact 1: a car engine usually converts gasoline into motion and heat through combustion. 
Fact 2: Combustion is never complete in gasoline and diesel engines.
Cars never completely convert gasoline into motion.

Fact 1: All chemical reactions require activation energy to get started. 
Fact 2: Chemical equations describe chemical reactions.

Chemical equations describe something that requires activation energy to get started.

