It is often the case that the yield curve inverts and portends a recession in the United States of America: however, which of the following is not true with respect to the yield curve? (Select all that are true, could be more than one)

a. The yield curve shows yields on various maturities of US treasuries organized with increasing maturity on the x-axis, and yields (return) of those treasuries on the y-axis

b. The yield curve can be used to infer changes in risk appetities of investors as long- and short- term rates shift.

c. The yield curve shows the real-rate of interest in the US across various maturities.

d. The yield curve always correctly predicts a recession in the case of inversion---it has never been wrong.