The term ‘osmotic pressure’ was coined by Pfeffer.
It is the pressure which is applied at the solution side to prevent the movement of solvent particles towards the solution.
The osmotic pressure is equal and opposite to the force applied by the solvent particles.
It can be defined as the excessive hydrostatic pressure which must be applied to the solution in order to make its water potential equal to that of pure water.
In other words, it is the pressure which is needed to check the process of osmosis.
It can be measured by osmometer.
It is a positive force.
It is a colligative property.
Osmotic pressure is a positive pressure. Hence, the correct answer is option b.