Which sentence from the article best supports the text's main idea? A. "For 20 years, Stanford University Psychologist, Carol Dweck has been dedicated to demystifying the power of mindset." (Paragraph 4) B. "These kids saw the math problems as an opportunity to learn, rather than a litmus test of their personal value. They weren't concerned about looking bad or feeling stup." (Paragraph 9) C. "A fixed mindset creates the need to prove oneself. Deficiencies must be hidden since they can't be developed. Failure is to be avoided at all costs." (Paragraph 10) D. "Cultivating a growth mindset is like learning a new language. You've got to work at it every day, but with practice, it becomes more natural and, eventually, you become fluent." (Paragraph 16)