If the yield curve is upward sloping, which of the following statements is correct? Select one: a. The default risk premium on T-bonds decreases as years to maturity (T) increases. b. The maturity risk premium on T-bonds decreases as years to maturity (T) increases. c. The inflation premium on T-bonds could decrease with maturity (T). d. The liquidity risk premium on T-bonds decreases as years to maturity (T) increases. e. The real risk-free rate on T-bonds decreases as years to maturity (T) increases.