Answer:
D. Earth is between the sun and the moon
Step-by-step explanation:
During a full moon, we can obviously see the entire "circle" of the moon in the sky at night. That means that nothing can be blocking its light from reaching us. Another note is that the moon actually reflects the light of the sun, so the moon, Earth, and sun must all be oriented in a way that will maximize this reflectivity and ensure that the moon is seen.
The way that this occurs is when the Earth is between the moon and the sun (see attachment). As you can see, the sunlight is beaming onto the moon, which is facing the Earth, allowing us to see it.
Hope this helps!