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: Mammals generate heat mainly by keeping their metabolic rate high. 
Fact 2: Shrews have the highest metabolism of any mammal.

SOLUTION: Shrews generate the most heat by keeping their metabolic rate high.

PROBLEM: Fact 1: Adolescence is a time of significant mental, emotional, and social changes. 
Fact 2: Adolescence is a scary time for a teenager.

SOLUTION:
teenagers experience significant mental, emotional, and social changes.