Fact 1: Brain cells die quickly if their oxygen supply is cut off.

Fact 2: If the oxygen supply to the brain is cut off, a stroke can occur.

Given the two facts above, answer the question "What die quickly if a stroke occurs?" with the following options: 
- a fish
 - animals
 - brain cells
 - organs
 - critical organs
 - protons
 - neutrons
 - bones


 

   brain cells      