a$.$ The yield curve from February $2007$ slopes downward, meaning interest rates and maturity terms are inversely related.

b$.$ The yield curve from January $2008$ is characteristic of a normal yield curve, reflecting that the shorter the term, the higher the risk, and then interest rates decrease over time.

c$.$ The yield curve from February $2007$ is inverted as investors anticipated that inflation was likely to cause future short$-$term rates to be lower than current short$-$term rates.

d$.$ The yield curve from January $2008$ slopes upward, meaning interest rates and maturity terms are directly related.Maturity