Light year is the unit of

Options

A. speed
B. mass
C. distance
D. time

Answer

To determine what the unit "light year" represents, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding the Term "Light Year":**
- A light year is defined as the distance that light travels in one year. This is the fundamental definition that we need to consider.

2. **Analyzing the Components:**
- The term "light" refers to the speed of light, which is approximately \(3 \times 10^8\) meters per second.
- The term "year" refers to a time period, specifically one year.

3. **Calculating the Distance:**
- To find out how far light travels in one year, we can calculate it using the speed of light and the number of seconds in a year.
- There are \(365\) days in a year, and each day has \(24\) hours, each hour has \(60\) minutes, and each minute has \(60\) seconds.
- Therefore, the total number of seconds in a year is:
\[ 365 \text{ days} \times 24 \text{ hours/day} \times 60 \text{ minutes/hour} \times 60 \text{ seconds/minute} = 31,536,000 \text{ seconds} \]

4. **Calculating the Distance Light Travels in One Year:**
- Now, we can calculate the distance light travels in one year:
\[ \text{Distance} = \text{Speed} \times \text{Time} = (3 \times 10^8 \text{ m/s}) \times (31,536,000 \text{ s}) \approx 9.4607 \times 10^{15} \text{ meters} \]

5. **Conclusion:**
- Since a light year is defined as the distance that light travels in one year, it is a unit of distance.

### Final Answer:
The light year is a unit of **distance**.