Which of the following laser printer components will flip the paper to allow for printing on both sides?

The paper registration assembly aligns the paper and controls its timing as it enters the print path; it does not flip the paper.

The paper pickup assembly draws paper from the input tray at the start of the print cycle; it has no role in re-routing printed pages.

The duplex assembly is a dedicated paper path mechanism in a laser printer that receives the page after one side is printed and re-feeds it back through the imaging and fusing process in reverse orientation. This allows the printer to print on both sides of a sheet without manual intervention from the user.

The image transfer belt transfers toner from the photosensitive drum onto the paper; it is part of the imaging process, not the paper handling path.