I found your question in another source.
See attached image.
By definition we have:
P = d x h x g
where:
P = Pressure (N / m²)
d = Density (Kg / m³)
h = Height (m)
g = Force of gravity (m / s²)
We have to:
g = 9.8 (m / s²)
d = 1000 Kg / m³
Therefore the pressure only depends on the height.
We have then that the lowest pressure is at point A since that point represents the lowest height with respect to the surface:
h = 20m
Answer:
A