Answer:
The correct answer is - concentration of blood plasma proteins.
Explanation:
The blood colloid osmotic pressure or oncotic pressure is one of osmotic pressure that takes place by protein, especially albumin concentration in the plasma of blood vessels that expels water molecules.
It is a relative water deficit with water molecules or difference ECF between the protein and interstitial fluid of the that is termed as the oncotic pressure.
Thus, the correct answer - concentration of blood plasma proteins.