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Passage: For most of her career, the marine biologist Sylvia Earle was told that the deep ocean was a desert—too dark, too cold, and too crushing to harbor much life. When she finally descended in a submersible to the seafloor a mile down, she found instead a landscape glittering with bioluminescent creatures, more of them blinking and pulsing than she could count. The discovery did not merely add a few species to the catalog; it forced a generation of scientists to admit that their assumptions had been shaped by the limits of their instruments rather than by the ocean itself. What they had called emptiness, Earle realized, was only the boundary of what they had been able to see. Which of the following best states the main idea of the passage?

1. Earle's dive revealed that the deep ocean's apparent lifelessness reflected the limits of human observation rather than a true absence of life.
2. Bioluminescent creatures are far more numerous on the seafloor than anywhere else in the ocean.
3. Submersibles allowed scientists to finally reach the coldest and darkest regions of the sea.
4. Sylvia Earle spent most of her career studying deserts before turning to marine biology.

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