Answer:
a. privilege escalation
Explanation:
Privilege escalation is the act of exploiting a bug, design flaw or configuration oversight in an operating system or software application to gain elevated access to resources that are normally protected from an application or user.
Thus, if a user without administrative privileges was able to perform a task limited to only administrative accounts, this can be called as privilege escalation.
DNS cache poisoning is a type of attack that exploits vulnerabilities in the domain name system (DNS) to divert Internet traffic away from legitimate servers and towards fake ones.
A man-in-the-middle attack is an attack where the attacker secretly relays and possibly alters the communications between two parties who believe that they are directly communicating with each other.
ARP poisoning is a technique by which an attacker sends Address Resolution Protocol messages onto a local area network.