Final answer:
c) Trojan Horse is a malicious program that gives unauthorized control or starts an unauthorized task, while masquerading as legitimate software, different from viruses, worms, and rootkits.
Step-by-step explanation:
A Trojan Horse is a type of malicious software program that gives someone remote, unauthorized control of a system or initiates an unauthorized task, often while disguised as a legitimate program. Unlike a virus, which attaches itself to clean files and spreads through the file system, a Trojan horse appears as a normal file and tricks the user into running it, thereby executing the unauthorized activities. A rootkit, on the other hand, is designed to give continued privileged access to a computer while concealing its existence, and a worm is a standalone malware that replicates itself in order to spread to other computers.