The correct answer is: C. Misalligned print head.
A dot matrix printer prints text and images by striking an inked ribbon against paper. The print head contains a series of pins that strike the ribbon, which then transfers the ink to the paper. If the print head is misaligned, the pins will not strike the ribbon evenly, resulting in light and dark areas on the printed page.
Erratic paper advancement can also cause light and dark areas on the printed page, but this is usually due to a problem with the printer’s paper feed mechanism. Overheating of the print head can also cause problems with print quality, but this is usually more noticeable as smudging or uneven ink coverage.
None of the other options are correct.