Given the task definition and input, reply with output. In this task, you are given two facts, and a multiple-choice question. Based on the given facts, answer the question with index of the correct option (e.g, "A").

Fact1: Cancer is a disease that occurs when the cell cycle is no longer regulated., Fact2: Brain tumors are one of the fastest growing cancers today., Question: Brain tumors occur when what is no longer regulated? (A) fossil fuels (B) headaches (C) voltage (D) heat or cold (E) cell cycles (F) critical organs (G) cerebellum (H) migraines
E