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.

Input: Consider Input: Fact 1: faulting of rock in Earth 's crust causes earthquakes. 
Fact 2: Earthquakes generate P waves and S waves which can travel throughout the earth.

Output: P-waves and S-waves can be traced back to faulting of rock in Earth's crust.


Input: Consider Input: Fact 1: a warm front causes cloudy and rainy weather. 
Fact 2: Behind the warm front are thick, low stratus clouds and possibly more rain.

Output: cloudy and rainy weather is accompanied by stratus clouds.


Input: Consider Input: Fact 1: howling is used to warn other wolves by wolves. 
Fact 2: And somewhere a beagle howls a most pitiful sound.


Output: wolves use sound to warn other wolves.