Which of the following describes a characteristic of laser printers?

Laser printers are characterized primarily by their use of powdered ink, known as toner. This toner is a fine powder that is fused to paper using heat and pressure during the printing process. This method allows laser printers to produce high-quality images and text with precise detail and sharpness. The powdered nature of the toner differentiates laser printers from inkjet printers, which utilize liquid ink to create prints.

Given the other options, while some printers might use liquid ink and there are printers that can print in color, laser printers specifically rely on powder rather than liquid. They do not require an external cooling system, as they are designed to operate efficiently without one. Therefore, the key characteristic of laser printers is their use of powdered ink, making this the correct choice.