5) Which one/s of the following features characterize correctly the APT model? a. The concept of market portfolio plays a key role in the model. b. Each stock' s return depends partly on pervasive macroeconomic influences or factors and partly on noise. c. Unique risk can' t be eliminated through diversification. d. The risk premium on a stock depends on the expected risk premium associated with each factor and the stock' s sensitivity to each of the factors