Why is C wrong?

Hi Jing Jing, The main issue with this argument is that there is no reason for the passage to be describing the portion of the brain that is known to be useless as a "tremendous source of creativity and innovation". The author makes no effort to justify that this unused/useless 90 percent will translate to being a source of creativity or innovation. C is wrong because the argument did not state that 90 percent of the brain serves no function because "we do not know what this 90% does". Rather it explicitly states that we know it is useless based on the conditions of many people with brain damage. I hope this helps. Please let me know if you'd like me to elaborate further!