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: Echinoderms use pheromones to communicate with each other. 
Fact 2: Ascothoracican barnacles attach to echinoderms or corals.

SOLUTION: corals use pheromones to communicate with each other.

PROBLEM: Fact 1: Pneumonia may be caused by an infection or injury of the lungs. 
Fact 2: Infections of the lungs can be caused by bacteria, viruses or fungi.

SOLUTION: Pneumonia may be caused by viruses or injury.

PROBLEM: Fact 1: Blood pH may become unbalanced if the rate of breathing is too fast or too slow. 
Fact 2: Slow and fast respirations or long periods without a breath are common in the dying child.

SOLUTION:
Blood pH may become unbalanced if respiration is too fast or too slow.