Barbara is a mortgage broker, who is paid by commission. When interest rates decline, she does a lot of business and earns a lot of money, as more people buy houses or refinance their mortgages. But when interest rates rise, business falls substantially. To diversify, Barbara should choose investments that a. provide a lower return than the market average. b. provide a higher return than the market average. c. pay lower returns when interest rates rise and higher returns when interest rates fall. d. pay higher returns when interest rates rise and lower returns when interest rates fall.