It is an entity or event with the potential to adversely impact a system through unauthorized access, destruction,
disclosure, denial of service or modification of data.
Which of the following terms best matches the definition?

A.
Threat

B.
Attack

C.
Vulnerability

D.
Risk

Explanation:
A threat is a any circumstance or event with the potential to adversely impact organizational operations
(including mission, functions, image, or reputation), organizational assets, or individuals through an information
system via unauthorized access, destruction, disclosure, modification of information, and/or denial of service.
Also, the potential for a threat-source to successfully exploit a particular information system vulnerability.
https://en.wikipedia.org/wiki/Threat_(computer)