p=FS=GS=mgS=ρVgS=ρgh。

(2) p = fs = GS = MGS = ρ vgs = ρ GH。

∵ The pressure of two objects on the horizontal plane is the same, that is, p=ρAghA=ρBghB,

∴ρAp-ρBgh，

That is, pa > Pb, so d is wrong;

(3)∵A's pressure on the ground is equal to B's pressure on the ground.

∴ ρ A < ρ B can be obtained by p=ρgh.

When the same thickness is cut in the horizontal direction at the upper part of two objects,

The side of a is longer than the side of b,

∴ The bottom area of A's is larger than that of B, and the cutting width in the vertical direction is the same.

The bottom area of a' is larger than that of B',

∴ The mass △mA of the truncated part must be greater than △mB, so A is wrong;

(4) The side of A is longer than the side of B,

∴ The bottom area of A's is larger than that of B. When the upper parts of two objects are cut to the same thickness in the horizontal direction,

The bottom area of a' is larger than that of B',

∫F = PS，

A' pressure on the ground must be greater than B' pressure on the ground.

∴ The mass Ma ′ of the rest must be greater than MB ′. Therefore, B is correct.

So choose B.