Which type of malware is designed to replicate itself and spread to other systems?

The correct choice is a virus because a virus is specifically designed to replicate itself and spread to other systems. It attaches itself to legitimate software or files and, when activated, can copy itself and infect other files on the same or additional systems. This self-replicating nature enables it to spread widely, often without the user's knowledge or consent.

Conversely, spyware is designed to collect information from a user's device without their knowledge, a Trojan horse masquerades as a legitimate program to deceive users into installing it but does not replicate itself, and ransomware encrypts a victim's files and demands a ransom, primarily focusing on extortion rather than replication. Thus, the defining characteristic of a virus being able to replicate and spread distinguishes it from these other types of malware.