The correct answer is: A. HSLa Color
HSLa is a color model that represents colors using hue, saturation, lightness, and alpha. Hue is the color’s angle on the color wheel, saturation is the color’s intensity, lightness is the color’s brightness, and alpha is the color’s opacity.
RGB is a color model that represents colors using red, green, and blue. Each color is represented by a value between 0 and 255, where 0 is the absence of the color and 255 is the full intensity of the color.
RGBa is a color model that is similar to RGB, but it also includes an alpha channel. The alpha channel represents the color’s opacity, where 0 is fully transparent and 255 is fully opaque.
In conclusion, HSLa is the color format that is the CSS3 HSL value with a fourth value to set the alpha channel value for the color to define the opacity of the element.