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: most canyons are formed by flowing rivers through erosion over long periods of time. 
Fact 2: Canyon Lake Canyon lake was formed by dams on the Salt River.
Example Output: dams can form canyons.

Example Input: Fact 1: a fire requires oxygen to burn. 
Fact 2: There is no "gaseous" oxygen on the Moon and the Moon itself is bone dry.
Example Output: A fire is cannot burn naturally above the surface of the Moon.

Example Input: Fact 1: travelling requires navigation. 
Fact 2: For celestial navigation the navigator uses a sextant and a chronometer.
Example Output:
Travelling requires a tool such as a sextant.

