Fact 1: Constriction occurs when the muscular walls of blood vessels contract.

Fact 2: Cocaine constricts the blood vessels.

Given the two facts above, answer the question "Cocaine causes what to contract?" with the following options: 
- layers of fat
 - a lot of human deaths
 - Walls of blood vessels.
 - harmful substances
 - the rest of the body
 - metabolic reaction
 - direct damage to the lungs
 - decreases its bodily water


 

   Walls of blood vessels.      