Final answer:
The correct statement supported by the phosphorus cycle diagram is that 'Phosphorus primarily cycles through water bodies.' It describes how phosphorus enters aquatic ecosystems and participates in marine food webs before settling as sediment in the ocean.
Step-by-step explanation:
The question asks which statement is best supported by the diagram of the phosphorus cycle. According to the provided information, phosphorus in nature exists as the phosphate ion (PO4³-), which is released into the environment through weathering of rocks and volcanic activity. From there, it enters soil, water, and becomes available to food webs. It specifically mentions that phosphate is not taken up directly from the atmosphere by plants but is absorbed by them from the soil. The phosphorus enters the oceans through various ways, including surface runoff, groundwater flow, and river flow, and is integrated into marine food webs. Some of it settles on the ocean floor, forming sediments that can be uplifted over time to become part of terrestrial ecosystems again.
Given this information, the correct answer to the question is 'b. Phosphorus primarily cycles through water bodies.' This is because the cycle involves phosphorus entering waterways and the ocean, participating in marine food webs, and eventually settling as sediment.