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: a camera is used for recording images. 
Fact 2: Movies are images and moving pictures.

SOLUTION: A camera is used for recording still and moving pictures.

PROBLEM: Fact 1: Some viruses have an envelope of phospholipids and proteins. 
Fact 2: Viruses are enveloped by similar membranes.

SOLUTION: viruses have similar membranes.

PROBLEM: Fact 1: a cavern is formed by carbonic acid in groundwater seeping through rock and dissolving limestone. 
Fact 2: Caverns Secrets are hidden in caves.

SOLUTION:
hidden caves are formed by carbonic acid in groundwater seeping through rock and dissolving limestone.