A scientist is investigating how the amount of available water affects plant growth in a rainforest. Although all of Earth's spheres are interconnected, which of Earth’s spheres does the scientist’s investigation focus on?

Available water is part of the hydrosphere, and plants are living things in the biosphere. Since the investigation examines how water availability affects plant growth, it focuses on the hydrosphere and the biosphere. The geosphere is Earth’s solid land and rocks, so choices involving it do not best describe the investigation.

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