If the yield curve is upward sloping, then wuch type of marketable securitas assumed to be held for emergencies, should be held in a firm's portfolio? O a. They should consist mainly of short-term securities because these pay higher rates b. They should consist mainly of short-term securities to minimize interest rate risk O They should consist mainly of government securities to minimize interest rate tisk d. They should consist mainly of long-term securities because those pay higher rates