Final answer:
When a malicious file is quarantined, it is moved to a secure location on the device to prevent it from causing further harm to the system.
Step-by-step explanation:
When a malicious file is manually quarantined on a device, the correct answer is b) It is moved to a secure location on the device. Quarantining a file involves isolating it to prevent the spread of potential harm it might cause to the system. This secure area restricts the file's ability to execute or interact with other parts of the system, thereby containing the threat until further action is taken, such as removal or further analysis.