Final answer:
The correct description of a total solar eclipse seen on the moon is when the Moon passes between the Earth and the Sun, which results in the Moon casting its umbra onto Earth, completely blocking the Sun for observers in the shadowed area.
Step-by-step explanation:
The best description of a total solar eclipse seen on the moon is A) The moon passes between the Earth and the sun. This is because a total solar eclipse occurs when the Moon is close enough to Earth and aligns perfectly between the Sun and Earth, causing the Moon's umbral shadow to fall onto Earth's surface.
Those within this small shadowed area experience the eclipse in totality, seeing the Sun completely obscured by the Moon and the Sun's corona becoming visible. Conversely, during a lunar eclipse, the Moon moves into the shadow cast by Earth and is visible from the Earth's night hemisphere.