According to your understanding of the risk-return concept. Which of the following portfolios has the least risk? Select one: a. A portfolio of long-term U.S. government bonds b. A portfolio of U.S. common stocks of small firms c. A portiolio of Treasury bills. d. A portfolio of U.S. common stocks of large firms When the interest rate tises, the value of financial assets is expected to a. increase b. decrease c. interest rales don't chango d. no change cletar my choice