Which of the following defines the net filtration pressure (NFP)?
(a) BCOP - (GHP + CHP)
(b) GHP - (BCOP + CHP)
(c) (BCOP + GHP) - CHP
(d) (GHP - CHP) + BCOP

The correct answer is (a) BCOP-\left( GHP+CHP \right) .

Net Filtration Pressure (NFP) is the force responsible for moving fluids across the capillary walls during filtration in the capillaries of the circulatory system. It's the difference between the forces that promote filtration and the forces that oppose filtration.

NFP is calculated as follows:
NFP = (Hydrostatic Pressure in the Glomerulus) - (Osmotic Pressure due to Blood Colloid Osmotic Pressure) - (Hydrostatic Pressure in Bowman's Capsule)

In the given options:

GHP represents the Glomerular Hydrostatic Pressure (the blood pressure in the glomerulus).
BCOP represents the Blood Colloid Osmotic Pressure (the osmotic pressure due to proteins in the blood).
CHP represents the Capsular Hydrostatic Pressure (the hydrostatic pressure in Bowman's capsule, opposing filtration).
So, the correct formula is BCOP - (GHP + CHP). This is because the Glomerular Hydrostatic Pressure and the Capsular Hydrostatic Pressure oppose the filtration, while the Blood Colloid Osmotic Pressure promotes filtration. The net effect of these pressures determines the net movement of fluid across the capillary walls.