During the coronavirus pandemic, Marriott International, Inc. filed a Form 10-K with the Securities and Exchange Commission that included the following statement: "COVID-19 has negatively impacted, and will in the future negatively impact to an extent we are unable to predict, our revenues from managed and franchised hotels, which are primarily based on hotels' revenues or profits." What action has Marriott taken in making this statement?
a) Disclosure of a material risk
b) Explanation of risk appetite
c) Demonstration of zero-tolerance
d) Over-regulation