6. Spherical polar coordinates are used in the solution of the hydrogen atomSchrodinger equation because
(A) the Laplacian operator has its simplest form in spherical polar coordinates.
(B) Cartesian coordinates would give particle-in-a-box wave functions.
(C) the Schrodinger equation is then separable into 3 ordinary differentialequations.
(D) Otherwise the atomic orbitals would violate the Pauli Exclusion Principle.
(E) Schrodinger first used this coordinate system； any other coordinate systemwould be equally convenient.