Which of the following statements is true?
A. We can determine the exact location of an electron if we know its energy.
B. An electron in a 2s orbital can have the same n, l, and ml quantum numbers as an electron in a 3s orbital.
C. Ni has two unpaired electrons in its 3d orbitals.
D. In the building up of atoms, electrons occupy the 4f orbitals before the 6s orbitals.
E. Only three quantum numbers are needed to uniquely describe an electron.