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: Humans have collected and grown mushrooms for food for thousands of years. 
Fact 2: Yeast and mushrooms are types of fungus.

SOLUTION: Humans have collected and grown fungus for food for thousands of years.

PROBLEM: Fact 1: a planet rotating causes cycles of day and night on that planet. 
Fact 2: Rotation determines day and night, and the length of the day.

SOLUTION: a planet's rotation is what causes night.

PROBLEM: Fact 1: natural magnetism is used for pointing north by a compass. 
Fact 2: Additionally, a surveyor s compass was used.

SOLUTION:
Natural magnetism is used for pointing north in a surveying tool.