Which one is the correct answer?
The answer is E. pg(H-h)S, upwards
What question wants is Force, right?
So, A,B & D are not available anymore since they are Pressures.
So, we are left with C and E. By Pascal’s law, the pressure exerted on both side of the valve in a pipe are the same, however, we don’t have valve or piston on the other end. But we know that the pressure and area (given) are the same, the force must be the same.
In order to describe the force in terms of density,
F = rho g V
F = rho g A h
F = rho g S (H-h) because the area and here is the area of the valve not the area of the pipe and the same goes for height inserted here.