2. Over the last 50 years, stock prices have vacillated up and down, with occasional sud- den and significant moves in response to external shocks, but without any discernible cycles. Overall, however, the average return has exceeded the riskless interest rate. This is consistent with (a) an efficient stock market populated by risk-loving investors setting a time-varying expected return (b) an inefficient stock market populated by risk-loving investors setting a constant expected return (c) an efficient stock market populated by risk-averse investors setting a time-varying expected return (d) an inefficient stock market populated by risk-averse investors setting a constant expected retum EXPLANATION