Final answer:
The statements about the historical S&P 500 returns are false because the 1-year returns have been both lower and higher than the range given, and the lowest 20-year average return was not -3.0%.
Step-by-step explanation:
The historical S&P 500 1-year returns from 1928 - 2016 have shown significant variation, but not within the narrow range of approximately 25% to -15% as the returns have been both above and below those figures. For instance, in 2008, the S&P 500 declined by about 37%, while in 2009, it increased by approximately 26%. Looking at the lowest 20-year average return for this period, it is not as low as -3.0%, indicating that over any 20-year period, the S&P 500 did not average an annual loss. Taking these points into consideration, the correct statement is that both claims a and b are false.