Chordates have a complete digestive system and a closed circulatory system, and because reptiles are vertebrates, they are chordates. Given these facts, vertebrates have a complete digestive system and a closed what among the following options:
- digestive tract
 - lung system
 - the body's largest organ
 - circulatory system
 - Veins and arteries.
 - brain stem
 - all liquids
 - major threat to health


 

    circulatory system     