追溯。 Hints： volcano sulphurous whereas

The earth would have been covered in volcanoes and billowing vents of steam and sulphurous water.
Had you been standing here, you'd have been present as the story of life was unfolding. And had you been standing here, you'd have been standing by the most advanced life form on the planet. In this almost boiling water, there are thousands of long thin strands. They are actually colonies of tiny heat loving creatures, they are bacteria. Once, long ago, this was the most complex form of life anywhere on earth. What's so surprising is that it's still here today, just like it was three billion years ago. Whereas dinosaurs came and went, and literally millions of other species developed, withered and died out, this has survived practically unchanged.

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