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: skin is used for breathing air by frogs. 
Fact 2: Air contains oxygen.

SOLUTION: skin is used for breathing oxygen by frogs.

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 pan is used for cooking food by heating food in it on a stove. 
Fact 2: Stoves Stoves can be a source of many accidents in the kitchen.

SOLUTION:
A pan is used for cooking food by heating food in it on a source of many accidents in the kitchen.