Fact 1: Chordates have a complete digestive system and a closed circulatory system.

Fact 2: Vertebrates are members of of a larger group, the chordates .

Given the two facts above, answer the question "vertebrates have a complete digestive system and a what?" with the following options: 
- Veins and arteries.
 - lack of backbone
 - bruised brain stem
 - critical organs
 - closed circulatory system
 - incomplete circulatory system
 - characteristics
 - sensory neurons


 

     closed circulatory system    