We Can Understand How Pressure in Water Depends on Depth

We can understand how pressure in water depends on depth by considering a stack of bricks. The pressure at the bottom of the first brick corresponds to the weight of the entire stack. Halfway up the stack, the pressure is half because the weight of the bricks above is half. To explain atmospheric pressure, we should consider a similar scenario but with compressible bricks made from a material like foam rubber. Why?

A) Water is not very compressible, but air is.
B) There is a lot more space between the molecules in air than there is between the molecules of liquid water.
C) The density of air decreases as one comes down a mountain.
D) all of the above