You are presented with the question "What does caffeine do to blood vessels?" and the following answer choices: 
- It expands
 - looseness
 - hydrate their cells
 - Constrict them
 - sweating
 - Dehydration
 - They may not survive.
 - Damages them

Now knowing that caffeine is a central nervous system stimulant and caffeine is a stimulant, and a stimulant constricts blood vessels, choose the best answer.


 

    Constrict them     