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.

Fact 1: Protozoa make humans sick when they become human parasites. 
Fact 2: Malaria parasites are transmitted by mosquitos.
Malaria is a protozoa that make humans sick.

Fact 1: coal is used for generating heat by burning. 
Fact 2: Thus, the food is cooked by heat generated internally.
coal can be used to cook food.

Fact 1: All chemical reactions require activation energy to get started. 
Fact 2: Catalysts lower the activation energy.

A catalyst can lower the energy cost of a chemical reaction.