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.

Example Input: Fact 1: Pneumonia may be caused by an infection or injury of the lungs. 
Fact 2: Infections of the lungs can be caused by bacteria, viruses or fungi.
Example Output: Pneumonia may be caused by viruses or injury.

Example Input: Fact 1: Most species go through larval stages after hatching. 
Fact 2: Geckos hatch from eggs.
Example Output: Geckos go through larval stages while growing.

Example Input: Fact 1: Carbon monoxide is a gas produced by furnaces and other devices that burn fuel. 
Fact 2: Any fuel that is incompletely burned produces carbon monoxide, a colorless, odorless gas.
Example Output:
Fuel that burns incompletely in a furnace creates carbon monoxide.