Which action supports an effective printer preventive maintenance program?

Explanation:

The question asks which action supports an effective printer preventive maintenance program. Among the given options, the best action that supports an effective printer preventive maintenance program is to clean inkjet print heads when they stop working. It is important because it ensures that the nozzle of an ink-jet printer, which produces small ink droplets sprayed with electrostatic charge, remains clear and free of clogs, thus maintaining print quality and preventing potential damage to the printer.

For laser printers, which use a dry black powder called toner, it is not advisable to replace the toner at set predetermined time intervals without considering the actual toner level or print quality. Instead, toner should be replaced as needed based on print output and toner levels. Disconnecting the printer from its power source when not in use is generally not necessary as a maintenance step, and resetting the printer page counters may be helpful for monitoring but does not directly contribute to preventive maintenance.