Answer:
The answer is A: Earth casts a shadow on the moon.
Step-by-step explanation:
A lunar eclipse occurs when the earth passes between the sun and the moon, and the three of them are aligned. As the light of the moon that we see from the earth is actually the reflection of the sun's rays on it, when the earth is between the moon and the sun, it doesn't let the sun's rays to reach the moon, so what we see is the shadow of the earth over the moon.