In an ecosystem, phosphate levels are usually low because: phosphorous reacts with oxygen animals use all the available phosphates phosphorous is stored in the atmosphere the weathering of rock is a slow process

The correct answer is option D

The phosphate is found in lower amounts in environment because they are not present freely in the atmosphere. There are present in very small amount in the the rocks and the weathering of rock is a very slow process.

As it is a very slow process and because of this reason the phosphorous or the phosphate level in the ecosystem is very low.  

answer; hypnagogic sensations)