If reptiles are a class of tetrapod vertebrates that produce eggs with a waterproof shell, then reptiles are a class of tetrapod vertebrates that produce eggs with what?

Answer choices:
- empty shell
 - Chemical energy
 - waterproof shell
 - water-filled shell
 - aerobic capacity
 - heat energy
 - kinetic energy
 - shell lining

 

   waterproof shell       