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: Hormones control many cell activities, so they are very important for homeostasis. 
Fact 2: Temperature regulation is an example of homeostasis.

SOLUTION: Hormones are important for temperature regulation.

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: if fossils of a water animal or plant are found in a place then that place used to be covered by water in the past. 
Fact 2: Common fossils include plant fossils like ferns.

SOLUTION:
If a fern fossil is found then that places was previously covered in water.