Final answer:
The option that relates to the brightness of an object is luminance, which is the measurable amount of light output or reflected from a surface. Shape does not directly affect brightness. Brightness is indicated by luminous flux or illuminance, measured in lumens or lux, respectively.
Step-by-step explanation:
When determining the possible options for brightness, luminance is a relevant concept. Luminance refers to the measurable amount of light emitting or reflecting from a surface, often quantified in terms of lumens or candela per square meter. Contrarily, shape does not directly influence the brightness, but it can affect how light is distributed or perceived in a space. Brightness in a practical sense, when comparing light bulbs for example, should be assessed by looking at their rated luminous flux or illuminance on their packaging labels, which are quantified in lumens or lux. Artists may render the illusion of light and shadow through various techniques, manipulating value to convey a sense of luminosity. In the context of celestial objects, luminosity is paramount to understanding their intrinsic brightness and estimating distances in space based on their apparent brightness.