Considering a pyramid with a square base

Considering a pyramid with a square base, the solid angle of the vertex of the Pyramid (1 steradian) is defined as the ratio between:

A) the spherical surface that intersects the base of the pyramid in the central part,

and the square of the Radius of the sphere of Radius R whose length is equal to the height of the pyramid

B) the spherical surface that intersects the base of the pyramid on the two sides (at the margins),

and the square of the radius R of the sphere (whose length is equal to the height of the pyramid)

or

C) is it the ratio between the area of ​​the square base of the pyramid and the height?