The correct answer is option 'C' - The Sun.

Explanation:
The Sun is the only one among the given options that has its own light. Let's understand this in detail:

- The Earth: The Earth does not have its own light. It reflects the light from the Sun. During the day, when the Sun is visible, it appears bright because of the sunlight that reaches the Earth's surface. However, at night, when the Sun is not visible, the Earth's surface appears dark.

- The Moon: The Moon does not have its own light either. It reflects the light from the Sun, just like the Earth. When we see the Moon shining in the sky, it is because the Sun's light is illuminating it. However, during a lunar eclipse, when the Earth comes between the Sun and the Moon, the Moon can appear dark because it is in the Earth's shadow.

- The Sun: The Sun is a star that emits its own light. It is a massive ball of hot gases, primarily hydrogen and helium, undergoing nuclear fusion in its core. This fusion process releases an enormous amount of energy in the form of light and heat. The Sun's light illuminates the solar system, including the Earth and the Moon.

In conclusion, the Sun is the only celestial body among the given options that has its own light. The Earth and the Moon reflect the Sun's light, but they do not emit light on their own.