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 protecting the body from harmful substances. 
Fact 2: Contamination is the unintended presence of harmful substances or microorganisms in food.

SOLUTION: The skin is used for protecting the body from contamination.

PROBLEM: Fact 1: breaking apart rocks can cause debris. 
Fact 2: Examples of such rock include sandstone and shale .

SOLUTION: breaking apart sandstone can cause debris.

PROBLEM: Fact 1: Plants release oxygen during the day but not during the night. 
Fact 2: All orange trees are plants.

SOLUTION:
Orange trees release oxygen during the day but not at night.