Answer: D. reduce the unsystematic risk to a level where the unsystematic risk of one security is unrelated to the unsystematic risk of any other security held within the same portfolio.
Step-by-step explanation:
The Arbitrage Pricing Theory (APT) model allows for the forecasting of the returns on an asset by using the linear relationship between the returns of the asset and macroeconomic factors that relate to systematic risk.
It uses a multi-factor model to price securities and enables analysts to reduce unsystematic risk such that the unsystematic risk of one security is unrelated to that of another security in the same portfolio.