Which term denotes the distance light travels in one year?

• A. Astronomical Unit (AU)
• B. Absolute brightness
• C. Apparent magnitude
• D. Light year

Answer: (D)

The distance light travels in one year is called a light year, a unit of distance used in astronomy. Light moves about 299,792 kilometers every second, so in a year it covers roughly 9.46 trillion kilometers (about 5.88 trillion miles). This makes it a convenient way to express the vast distances between stars and galaxies.

Why this is the best answer: it directly defines the distance light travels in a year, which is exactly what the term describes. The other terms measure different ideas: the astronomical unit is the average distance from the Earth to the Sun and is used for solar-system scales; absolute brightness refers to how bright an object would appear at a standard distance (intrinsic luminosity), not a distance; apparent magnitude is how bright the object looks from Earth, which depends on distance and other factors, not a distance unit.