At a given point of time, the following quotes were observed in the markets: the S&P500 index was 2999.36, and the S&P500 index futures expiring in three months was trading at 2992.00. Why was the futures price lower than the spot index value?

a) It is because investors had no confidence in the president of the U.S.

b) It is because investors were pessimistic about the U.S. economy.

c) It is because the risk free rate was lower than the dividend yield of the S&P500 portfolio.

d) It is because stock markets was in a downward trend.