The correct answer is C. Anti-virus software is set to scan your computer weekly.
Step-by-step explanation:
In technology, anti-virus software aims at identifying and stopping the actions of viruses that spread in the host and alter normal functioning leading to issues in cybersecurity or damages in the software of a technological device. Additionally, for anti-virus software to be effective, the software needs to be updated, perform routine scans daily or almost daily and scan all elements download. This implies, if the anti-virus software is set to scan your computer weekly this might not prevent a computer virus because a virus can infect your computer and be unnoticed for several days. Thus, the one that is least effective at preventing computer virus is "Anti-virus software is set to scan your computer weekly".