When yield curves are flat, short-term interest rates are above long-term interest rates. medium-term interest rates are above both short-term and long-term interest rates. short-term interest rates are about the same as long-term interest rates. long-term interest rates are above short-term interest rates.\?

Calculator can help you

d. all of the above are true.

the answer would be voluntary exchange -

"the act of buyers and sellers freely and willingly engaging in market transactions. moreover, transactions are made in such a way that both the buyer and the seller are better off after the exchange than before it occurred."

hope this : )

-shy