The correct answer is B. Change the fuser temperature.

According to CompTIA A+ Core 1 220-1201 objectives under Printers:

A laser printer fuses toner onto paper using heat and pressure. Thicker paper often requires a higher fuser temperature to properly adhere the toner.

If the output smudges on thick paper but prints fine on standard paper, adjusting the fuser temperature is the first step before performing more invasive maintenance or replacing parts.

Why the other options are incorrect:

A. Install a maintenance kit: Typically includes rollers, belts, and other parts; this is not the first action if the issue is temperature-related.

C. Clean the transfer roller: Cleaning may improve print quality, but smudging on thick paper usually relates to insufficient fusing heat.

D. Install an OEM toner cartridge: The issue is unlikely to be caused by non-OEM toner if standard paper prints correctly.