Which of the following risks are considered as systematic risk?

I. Short-term interest rate decreases unexpectedly.

II. The credit rating of Cybertron Inc. is suddenly downgraded.

III. Congress approves changes to the tax code that will decrease the marginal tax rate.

IV. Big Widgets quarterly earnings report, just issued, is above analysts expectations.

A.I

B.I, II, and III

C.II, III, and IV

D.I and III