Fact 1: Mollusks are invertebrates such as the common snail.

Fact 2: Snails are protected by a hard shell on their backs.

Given the two facts above, answer the question "What are some invertebrates protected by on their backs?" with the following options: 
- fur
 - parasites
 - barnacles
 - shells
 - coats
 - bones
 - bushes
 - Epidermis


 

    shells     