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: HIV infects and destroys helper T cells. 
Fact 2: Helper T cells are the critical link in our immune system.
HIV damages our immune system.

Fact 1: volcanic ash in the atmosphere decreases the temperature by blocking the sun. 
Fact 2: Most volcanic ash consists of fine, dusty particles.
Fine, dusty particles erupted from volcanos decrease the temperature by blocking the sun.

Fact 1: Glucose is used for energy by the cells of most organisms. 
Fact 2: Glucose, the sugar the body uses for fuel, is stored as glycogen.

Sugar is used for energry by the body is stored as glycogen.