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: Mammalian teeth are important for digestion. 
Fact 2: For instance, bacteria in the digestive tract helps glean the most nutrients from food.

SOLUTION: Mammalian teeth are important for gleaning nutrients from food.

PROBLEM: Fact 1: glass cause refraction of light. 
Fact 2: Refraction Refraction is the bending of light rays.

SOLUTION: Glass causes bending of light rays.

PROBLEM: Fact 1: a black hole is formed by a high-mass star collapses. 
Fact 2: Stars are on an outermost celestial sphere.

SOLUTION:
A black hole is formed when a high mass celestial body collapses.