What phenomenon occurs at a full moon when Earth is positioned between the moon and the sun?

When Earth is positioned between the moon and the sun, it leads to the phenomenon known as a lunar eclipse, specifically during a full moon. At this time, the moon is fully illuminated by the sun, and the Earth's shadow can cast over the moon if they are perfectly aligned. The primary effect of this alignment is the darkening of the moon as it passes through the Earth's shadow, which can give the moon a reddish hue (often referred to as a "blood moon").

The other options refer to different astronomical events. Solar eclipses occur when the moon is positioned between the Earth and the sun, blocking the sun's light. Bright and extensive auroras are caused by solar wind interacting with Earth's magnetic field, not related to lunar positions. Meteor showers are typically the result of Earth passing through a trail of debris left by comets and are not specifically linked to the alignment of the Earth, moon, and sun. Finally, planetary alignments describe the positioning of planets in relation to each other rather than their relation to Earth's position to the moon and sun.

The clear alignment during a full moon, when Earth is situated between the sun and the moon, leads to the illumination of the moon rather than the phenomena listed in the other choices.