Final answer:
An object appears red because it reflects red light and absorbs other wavelengths. The correct explanation is that the object absorbs all wavelengths of light except red.
Step-by-step explanation:
When an object appears to be red, it is usually because it reflects red light and absorbs other wavelengths. Option D correctly explains this observation: the object absorbs all wavelengths of light except red. When considering color reflection and absorption, remember that the perceived color of an object under white light depends on which wavelengths of light are reflected back to our eyes. For example, a blue filter allows blue light to pass through because it absorbs all visible light other than blue light. Conversely, something that is red will not absorb red wavelengths; rather, it will absorb other colors and reflect red.
Additionally, option A suggests that the object absorbs only green light, which is incorrect, as absorbing only green would not necessarily make the object appear red. Instead, an object appears red if it absorbs blue and green light, the other primary colors of light.