Tunicates reproduce sexually, and tunicates are sea creatures encased by tough membranes, reminiscent of tunics. Given these facts, sea creatures encased by what reproduce sexually among the following options:
- barnacles
 - refraction of light
 - layers of fat
 - Epidermis
 - tough membranes
 - ocean water
 - gastropod shells
 - epidermis and dermis


 

     tough membranes    