Reconstruct a question, answer pair from this explanation: Brain cells die quickly if their oxygen supply is cut off. If the oxygen supply to the brain is cut off, a stroke can occur. Brain cells die quickly if a stroke occurs.

Q:What die quickly if a stroke occurs?
Options:
- (A) a fish
- (B) animals
- (C) brain cells
- (D) organs
- (E) critical organs
- (F) protons
- (G) neutrons
- (H) bones
A:(C)