In which part of the Earth is phosphorus primarily found?

• A. Atmosphere
• B. Biosphere
• C. Lithosphere
• D. Hydrosphere

Answer: (C)

Verified step by step guidance

1. Understand the context of the question: Phosphorus is a chemical element that is essential for life and is part of many biological molecules, such as DNA and ATP.
2. Identify the four spheres of Earth mentioned: Atmosphere (the layer of gases surrounding Earth), Biosphere (the global sum of all ecosystems), Lithosphere (the rigid outer layer of the Earth, including the crust and upper mantle), and Hydrosphere (all the water on Earth's surface).
3. Consider where phosphorus is most commonly found in nature: Phosphorus is not found in a gaseous state in the atmosphere, and while it is present in living organisms (biosphere) and dissolved in water (hydrosphere), its primary source is mineral deposits.
4. Recognize that phosphorus is primarily found in the form of phosphate minerals in rocks and soil, which are part of the lithosphere.
5. Conclude that the lithosphere is the primary reservoir of phosphorus on Earth, as it contains the mineral deposits from which phosphorus is mined and cycled through the biosphere and hydrosphere.