The correct answer is C. Backdoors.
A backdoor is a method of bypassing normal authentication or security procedures on a computer or network. Backdoors are often created by attackers to gain unauthorized access to a system, and can be used to steal data, install malware, or launch further attacks.
Antiware is a term used to describe software that is designed to protect against malware. Antiware can include antivirus software, anti-spyware software, and anti-rootkit software.
Rootkits are a type of malware that gives an attacker full control over a computer. Rootkits are often installed by attackers who have gained access to a system through a vulnerability or by social engineering.
Malware is a term used to describe any type of software that is designed to damage or disable computers and computer systems. Malware can include viruses, worms, Trojan horses, ransomware, and spyware.