Final answer:
The correct size order from smallest to largest, considering the terrestrial planets and the Moon, is The Moon, Earth, Mars.
Step-by-step explanation:
In determining the correct size order from smallest to largest, we must consider the physical sizes of Mercury, Venus, Mars, and the Moon. From the details provided, the terrestrial planets Mercury, Venus, Earth, and Mars are known to be smaller worlds with solid surfaces and range in size with Mercury being the smallest and Mars being larger than both Mercury and Venus but smaller than Earth. When discussing the Moon, although not a planet, it is often compared in size due to its significance and comparable size to some of the smaller planets.
The correct size order is option B: The Moon, Earth, Mars. To clarify, the Moon is smaller than Earth, and Mars is larger than both the Moon and Mercury but smaller than Earth and Venus.