Question

possible points: 5
when you look up at the night sky, you can usually see the moon. but the amount of the moon which appears illuminated (lit up) varies from night to night. this is partly because we can not always see all of the moons surface which is actually illuminated by the suns rays.
how much of the moons surface is actually illuminated by the sun at any one time?
about one half of the moon is illuminated, except during an eclipse.
all of the moons surface is illuminated.
it varies throughout the month depending on the moons location compared to the earth.
only about one quarter of the moon is illuminated.

Explanation:

The Sun illuminates one half of the Moon's surface at all times, since the Moon is a sphere facing the Sun. Eclipses are exceptions: during a lunar eclipse, Earth blocks sunlight from reaching the Moon, so less than half is illuminated temporarily. The apparent illuminated portion we see from Earth changes (phases), but the actual illuminated surface (from the Sun's perspective) is consistently half outside of eclipses.

Answer:

About one half of the moon is illuminated, except during an eclipse.