Comprehensive and Detailed In-Depth Explanation: In laser printers, the fuser unit is responsible for melting the toner onto the paper using heat and pressure. If the toner rubs off easily, it's a clear sign the fuser is failing or not heating properly. Replacing the fuser will ensure the toner bonds correctly to the paper. * Option B (Drum): Transfers the image, but doesn't fuse the toner. * Option C (Developer roller): Applies toner to the drum - wouldn't cause toner to rub off. * Option D (Discharge lamp): Prepares the drum for a new image; not related to toner adhesion. CompTIA A+ Core 1 Exam Objective Reference: * Objective 3.7: Given a scenario, troubleshoot common printer problems.