Phosphorus cycle is
A. Gaseous cycle
B. Perfect cycle
C. Imperfect cycle
D. Party gaseous and partly sedimentary

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Hint: The phosphorus cycle is a biogeochemical cycle. The gaseous cycle is a cycle in which the reservoir is a natural atmosphere, in a perfect cycle the nutrients of the cycle are replaced as soon as they are utilized and in the sedimentary cycle, the reservoir is earth's crust elements and these cycles are imperfect cycles.

Complete answer: 1. The phosphorus cycle is an imperfect cycle because the main reservoir of phosphorus is rock, which contains it in the form of phosphate, and mainly because the amount of phosphorus is lost in the cycle and is not recyclable. Phosphorus is the most important component of biological membranes, nucleic acids, and cellular energy transfer systems. Many animals also need a good amount of this element to make shells, bones, and teeth. The natural reservoir of phosphorus is rock. When rocks are weathered, a minute amount of phosphorus dissolves in soil and is absorbed by plants. Herbivores and others obtain it from plants. Rock being it is the largest reservoir, it is gradually eroding and releasing phosphates to the ecosystem, much of it escapes to the sea and is deposited in the shallow sediments and part of it is lost to deep sediments. A lot of soil phosphates are lost through leaching. These lost phosphates go out of circulation and are available after long geological periods. The means of returning phosphorus to the cycle are not adequate to compensate for the loss.
Hence, the correct answer is Option C.

Note: Inorganic phosphate usually occurs in the insoluble form. It is dissolved by phosphate solubilizing bacteria. The dissolved fraction is absorbed by plants and converted to organic form. From plants, it travels to various trophic levels. In animals, it is also deposited as part of the skeleton. The organic phosphorus is returned to the soil through death and excretion.