Fact 1: Arteries generally carry oxygen-rich blood.

Fact 2: Energy levels can plummet due to lack of oxygen-rich red blood cells.

Given the two facts above, answer the question "_ are needed to maintain energy levels " with the following options: 
- Ligaments
 - follicles
 - hydration
 - environment
 - glucose
 - pores
 - exercise
 - Arteries


 

        Arteries 