Question

In the phosphorus cycle, phosphorus can recycle through waste products, decomposition, and of terrestrial and aquatic ecosystems.
food chains
the atmosphere
assimilation

Answer 1

Answer is - Assimilation

Reasoning - photosynthetic organisms such as Algae or Plants assimilation phosphorus into their cell. Which they later transfer it to animals whom consume which then starts the cycle.

I answered the same question in another post but here I'll post what I wrote with reasoning why.

Answer 2

Answer: Assimilation

Explanation: The assimilation of the phosphorous is found inside the terrestrial and aquatic animals.

The phosphorous is found to be present in the depth of ocean or under the rock. Over the time the rain carries away the phosphorous into water bodies.

The water containing phosphorus is taken by the aquatic animals and terrestrial animals it gets assimilated in the body cells.