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: using a gasoline engine requires burning gasoline. 
Fact 2: Gasoline and flammable liquid related burns, however, are a preventable problem.
using an engine requires burning flammable liquid.

Fact 1: heating a liquid can be used to identify that liquid 's boiling point. 
Fact 2: Pressure affects the boiling point of a liquid.
Pressure can increase or decrease the boiling point.

Fact 1: Skin color is another polygenic trait. 
Fact 2: Melanin is the skin pigment that gives the skin a tan color.

Melanin amount is a polygenic trait.

