Question: Brain tumors occur when what is no longer regulated?
Options:
- (A) fossil fuels
- (B) headaches
- (C) voltage
- (D) heat or cold
- (E) cell cycles
- (F) critical organs
- (G) cerebellum
- (H) migraines
Let's be accurate as possible and think step-by-step.

Show your work and conclude with the exact phrasing "Therefore, the final answer is [answer]." where [answer] is just the final number or expression that solves the problem.
user
Cancer is a disease that occurs when the cell cycle is no longer regulated. Brain tumors are one of the fastest growing cancers today. Brain tumors occur when the cell cycle is no longer regulated.
The answer: (E).