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1·One day, a little boy was walking on the planet.

有一天，一个小男孩在这个星球上行走。

2·One day, a little boy Jim was walking on the planet, when he passed a cave and noticed a small red flower inside.

一天，一个小男孩吉姆在这个星球上行走，当他经过一个洞穴时，他注意到里面有一朵小红花。

3·Scientists think there was probably water on the planet long ago.

科学家们认为很久以前在那个行星上可能有水存在。

4·That may sound like a description of every teenager on the planet.

这听起来可能像是对这个星球上每个青少年的描述。

5·For seven million years they lived on the planet as part of nature.

七百万年来，他们作为大自然的一部分在这个星球上生活。

6·Of course, that may sound like a description of every teenager on the planet.

当然，这听起来可能像是对这个星球上每个青少年的描述。

7·To begin with, they will have to find out whether life has ever existed on the planet of Mars in the past.

首先，他们必须搞清楚火星上是否曾经存在过生命。

8·This break in Earth's history is marked by a mass extinction, when as many as half the species on the planet became extinct.

地球历史上的这次重大灾难以物种的大量消亡为标志；当时，地球上多达一半的物种都灭绝了。

9·Polar bears are the largest land animals that eat meat on the planet.

北极熊是地球上最大的陆地肉食动物。

10·People either drive me away or avoid me when they see me. You must be the happiest bird on the planet.

人们看到我，要么把我赶走，要么躲着我。你一定是这个星球上最幸福的鸟了。