30. In most terrestrial ecosystems, phosphorus is often tightly cycled because:
(A) It has a large atmospheric pool.
(B) It is produced by nitrification.
(C) It is mainly supplied by weathering and lacks a major gaseous phase.
(D) It is highly volatile and easily lost to the atmosphere.
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統計: 尚無統計資料
統計: 尚無統計資料