题目内容：

    Usually, the Full Moon shines brightly all night long, lighting homes, trees, cities, and fields. Sometimes, though, a strange event happens. The Full Moon turns dark in a lunar eclipse. Lunar means “about the Moon”, and an eclipse is a blocking(遮蔽) of light.

A lunar eclipse often impresses people so much because the Moon is bright and nearby. It is the closest heavenly body(天体) to Earth. When the Moon turns dark, we notice! It’s closer to us than Mars or any other planet, and closer than the Sun or any other star. On average, the Moon is 239,000 miles away from Earth’s center. The Sun is almost 400 times farther.

What causes a lunar eclipse? The first key is that the Sun makes light, but the Moon doesn’t. When you see the Moon shining at night, you’re seeing sunlight bouncing off(反射) the Moon.

The second key is that the Moon, which is smaller than Earth, goes around us about once a month. Once a month, the moon is on the opposite side of Earth from the Sun. Then the Sun fully lights the side of the Moon that we see. We call this event a Full Moon. That’s when the Moon shines brightest.

The third key is that, during a lunar eclipse, Earth gets in the way. When you go outside on a sunny day, your body blocks some of the sunlight and casts a shadow(投射影子) over things that lie on the opposite side of you from the Sun. Earth also casts a shadow, and sometimes it falls on the Moon. Then we have a lunar eclipse.

A lunar eclipse happens only during a Full Moon, since that’s the only time when Earth is between the Sun and the Moon. Usually, though, there’s no eclipse because the Full Moon passes above or below Earth’s shadow.

阅读以上信息，用恰当的单词完成下面的短文，每空一词。

The article introduces “lunar eclipse” to us. First it tells us the 1. of “lunar eclipse”. Then it explains why people love watching a moon eclipse. On one hand, the changing of its 2. catches people’s attention. On the other hand, it’s easier for people to enjoy a moon eclipse because among the 3., the moon is the closest to the earth.

At last, the article shows three keys cause a lunar eclipse. The first key is that the sunlight is seen bouncing off the Moon at night. The second key is that there should be a full Moon. The third key is that the 4. casts a shadow over the moon. In a word, a lunar eclipse happens only during a Full Moon, since that’s the only time when the Sun, the earth and the Moon are in a 5..