There is a portfolio that consists of a single stock. Which of the following types of "risk" can be reduced as the stocks issued by other companies are added to the portfolio?

I. Unexpected operational loss due to a massive product recall related to the passenger airbags

II.Unexpected introduced new tax code that will impose higher corporate tax rates

III. Decline in the nation's economic growth expected for the next few year

IV. Resign of the firm's CEO due to his personal scandal