Final answer:
when the moon crosses the meridian at sunset, and it's in the eastern sky, it is in the First Quarter phase. Full Moon. the correct option is (B).
Step-by-step explanation:
The First Quarter phase occurs when the moon is 90 degrees east of the sun in the sky. When the moon crosses the meridian at sunset, it means it is at its highest point in the sky for that day. In this scenario, the sun is setting in the west, and the moon is directly opposite, in the eastern part of the sky.
The calculation involves understanding that the moon takes about 29.5 days to complete one full orbit around the Earth, passing through all its phases. During the First Quarter phase, it is one-fourth of the way through this orbit, or approximately 7.4 days after the New Moon.
Therefore, when the moon crosses the meridian at sunset, and it's in the eastern sky, it is in the First Quarter phase. This phase is characterized by half of the moon's disk being illuminated and is a transitional phase between the New Moon and the Full Moon.