Final answer:
The celestial bodies listed from smallest to largest based on their actual size in kilometers are: Asteroid, Moon, Earth, Sun, which corresponds to answer choice A.
Step-by-step explanation:
To list the celestial bodies from smallest to largest based on their actual size in kilometers, we must consider the average diameters of asteroids, the Moon, Earth, and the Sun. Asteroids can vary widely in size, but most are smaller than Earth's Moon. Ceres, the largest asteroid, has a diameter of about 946 km. The Moon's average diameter is 3,476 km. Earth is significantly larger with a diameter of approximately 12,742 km. The Sun is the largest among these celestial bodies with a colossal diameter of about 1,391,000 km.
Given these sizes, the correct order from smallest to largest is:
Therefore, the correct answer to the question is:
A. Asteroid, Moon, Earth, Sun