Fact 1: Most mollusks have shells.

Fact 2: Coral reefs and shells are made of calcium carbonate.

Given the two facts above, answer the question "What do mollusks contain?" with the following options: 
- harmful substances
 - Organic compounds
 - bacon
 - cayenne
 - acetic acid
 - dogs
 - Chlorophyll
 - Calcium carbonate


 

        Calcium carbonate 