The vascular pressure that declines from roughly 35 mm hg to about 18 mm hg is the

The correct answer is "capillary hydrostatic pressure".

The 35 mmHg is the pressure in the arterioles. This pressure will go down as there is an increase in resistance to blood flow in the arterioles before going to the capillaries. 18 mmHg capillary hydrostatic pressure is roughly the average of the arterial pressure and the venous pressure.