According to the liquidity preference hypothesis, which of the following statements is correct? a. If term structure of interest rate is flat, then future short-term rates are expected to keep unchanged. b. The return on investing a two-year bond equals the return of two one-year rollover investments. c. If term structure of interest rate is upward, then future short-term rates are expected to increase. d. If term structure of interest rate is downward, then future short-term rates are expected to decrease. e. The return on investing a two-year bond is less than the return of two one-year rollover investments