Which of the following statements accurately describes a $\mathrm{light}-\mathrm{year}$?

• A. A $\mathrm{light}-\mathrm{year}$ is a unit of time equal to one $\mathrm{year}$.
• B. A $\mathrm{light}-\mathrm{year}$ is the time it takes for $\mathrm{light}$ to travel around the $\mathrm{Earth}$ once.
• C. A $\mathrm{light}-\mathrm{year}$ is the distance between the $\mathrm{Earth}$ and the $\mathrm{Sun}$.
• D. A $\mathrm{light}-\mathrm{year}$ is the distance that $\mathrm{light}$ travels in one $\mathrm{year}$.

Answer: (D)

Verified step by step guidance

1. Understand that a light-year is a unit used in astronomy to measure very large distances, not time or orbital paths.
2. Recall that light travels at a constant speed in a vacuum, approximately \$3 \times 10^{8}$ meters per second.
3. Recognize that one year is a unit of time, specifically the time it takes for the Earth to complete one orbit around the Sun, about 365.25 days.
4. Combine these concepts: a light-year is defined as the distance light travels in the span of one year.
5. Therefore, the correct description of a light-year is that it is a unit of distance equal to how far light travels in one year.