Which software provides protection from destructive bits of code loaded onto a computer without the user's knowledge?

The correct choice is antivirus software because its primary function is to detect, prevent, and remove malicious software, including viruses and other types of harmful code that can be loaded onto a computer without the user’s consent. Antivirus programs regularly scan files and running applications to identify and mitigate threats, ensuring that the system remains secure from various types of malware that can damage or compromise data.

While antispyware focuses specifically on spyware—software designed to gather personal information without the user's knowledge—antivirus has a broader scope of addressing various types of malware, including worms, Trojans, and viruses, making it an essential tool for overall protection. Firewalls act primarily as a barrier to prevent unauthorized access to or from a private network, rather than focusing on cleaning or detecting malware already on a system. Anti-malware software also encompasses antivirus capabilities but generally refers to broader protections against different kinds of malicious software, including adware and ransomware. However, in the context of this question, antivirus software is recognized specifically for its role in counteracting destructive code.