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.

Q: Fact 1: Most mollusks have shells. 
Fact 2: Mussels are bivalve mollusks.

A: Most mussels have shells.
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Q: Fact 1: Mollusks reproduce sexually. 
Fact 2: Some mollusks have a shell.

A: some animals with shells reproduce sexually.
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Q: Fact 1: dropping an object into water causes vibrations in the water. 
Fact 2: When something vibrates, it causes the air around it to vibrate.

A:
dropping an object into water makes the air around it move.
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