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: natural magnetism is used for pointing north by a compass. 
Fact 2: Compasses point to the Magnetic Poles.

SOLUTION: Natural magnetism is used to point to the magnetic poles.

PROBLEM: Fact 1: a black hole is formed by a high-mass star collapses. 
Fact 2: Fundamentally, a black hole is invisible.

SOLUTION: a star collapsing can be invisible.

PROBLEM: Fact 1: Annelids are worms such as the familiar earthworm. 
Fact 2: Earthworms are annelids meaning segmented.

SOLUTION:
Worms such as the familiar earthworm are segmented.