The normal distribution is a symmetric, bell-shaped frequency distribution. If the variability of the returns on large-company stocks was to decrease over the long-term, you would expect which one of the following as related to large-company stocks to occur as a result? a. Increase in the risk premium b. Increase in the average long-term rate of return C. Increase in the 68 percent probability range of returns d. Increase in the standard deviation e. None of the above