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The average annual return over the period 1886-2006 for stocks that comprise the S&P 500 is 11.5%, and the standard deviation of returns is 17.5%. Based on these numbers what is a 95% confidence interval for 2007 returns? A. -23.5%, 46.5% B. - 13.5%, 36.5% O C. - 11.75%, 23.25% D. -8.5%, 31.5%