The correct answer is A. Luminance.
Luminance is the brightness of a pixel, while chrominance is the color of a pixel. Transparent and opaque are not relevant to this question.
Luminance is a measure of the intensity of light, and is often represented as a grayscale value. The higher the luminance value, the brighter the pixel. Luminance is important for displaying images and videos, as it allows the viewer to see the different shades of gray in an image.
Chrominance is a measure of the color of a pixel, and is often represented as a red, green, and blue (RGB) value. The higher the chrominance value, the more saturated the color. Chrominance is important for displaying images and videos, as it allows the viewer to see the different colors in an image.
Transparent and opaque are not relevant to this question, as they are not measures of brightness or color. Transparent objects allow light to pass through them, while opaque objects do not.