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: 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: hearing is used for sensing sound by animals. 
Fact 2: Sound waves enter the ear, and are then amplified.

SOLUTION: Animals use ears to hear.

PROBLEM: Fact 1: Carbon may be stored in sedimentary rock for millions of years. 
Fact 2: Marble is considered a carbonate rock .

SOLUTION:
Carbon may be stored in marble for years.