Which of the following statement completions is CORRECT? If the yield curve is upward sloping, then the marketable securities held in a firm's portfolio, assumed to be held for emergencies, should a. consist mainly of long-term securities because they pay higher rates. b. be balanced between long- and short-term securities to minimize the adverse effects of either an upward or a downward trend in interest rates. c. consist mainly of short-term securities because they pay higher rates. d. consist mainly of U.S. Treasury securities to minimize interest rate risk. e. consist mainly of short-term securities to minimize interest rate risk.