They are variables that cannot be changed or are purposefully not changed in an experiment.
The correct answer is Soluble phosphorous
Soluble phosphorus is a measure of orthophosphate (PO4), the
soluble and inorganic filterable fraction of phosphorus, which is the most
stable type of phosphate and it is the form directly used up by the plant
cells.
The coefficient for Fe will be 6, because the left side Fr equals 6.
Blood is just red.
Blue blood in diagrams is just used to distinguish between deoxygenated and oxygenated blood but there’s no such thing as hving blue blood.
