TASK DEFINITION: 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.
PROBLEM: Fact 1: volcanic ash in the atmosphere decreases the temperature by blocking the sun. 
Fact 2: Or a veil of tiny particles from a volcanic eruption can block the sun.

SOLUTION: volcanoes can block the sun.

PROBLEM: Fact 1: the gravitational pull of the Moon on Earth 's oceans causes the tides. 
Fact 2: The lower is the tide, the better is the wave.

SOLUTION: gravitational pull of the moon causes waves.

PROBLEM: Fact 1: matter vibrating can cause sound. 
Fact 2: All matter is made of molecules.

SOLUTION:
molecules vibrating can cause sound.