Which of the following is the best example of firm-specific risk?

a. A global pandemic causes major disruptions in the economy.

b. The Federal Reserve increases the money supply dramatically, leading to massive inflation.

c. AAA Pharmaceuticals withdraws a medication as it studies whether strokes five people suffered after taking the medication were related to the medication.

d. As an arctic blast descends on North America, most of the United States is blanketed in snow or ice.