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: Sponges have specialized cells called collar cells. 
Fact 2: Collar cells are the work horses of the sponge.

SOLUTION: Sponges have specialized cells that are work horses.

PROBLEM: Fact 1: a scale is used for measuring weight. 
Fact 2: All weights are in grams.

SOLUTION: a scale is used for measuring grams.

PROBLEM: Fact 1: Roundworms reproduce sexually. 
Fact 2: Nearly all species of roundworms reproduce by laying eggs.

SOLUTION:
roundworms have offspring by laying eggs.