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: Protozoa make humans sick when they become human parasites. 
Fact 2: Malaria parasites are transmitted by mosquitos.

SOLUTION: Malaria is a protozoa that make humans sick.

PROBLEM: Fact 1: Coral reefs provide food and shelter to many ocean organisms. 
Fact 2: Organisms or living beings are literally things that are alive.

SOLUTION: Coral reefs provide food and shelter to many ocean living beings.

PROBLEM: Fact 1: a cavern is formed by carbonic acid in groundwater seeping through rock and dissolving limestone. 
Fact 2: Carbonic acid dissolves limestone by separating the calcium and carbonate and creating a liquid.

SOLUTION:
Caverns are formed when acid dissolves limestone, creating a liquid.