Electron Shells Closest to the Nucleus Are Occupied Before Electron

Multiple Choice

Electron shells closest to the nucleus are occupied before electron shells farther from the nucleus because the electrons shells closest to the nucleus are

A) pulled toward the nucleus by gravity.
B) protected by the outer shell.
C) attracted to the nucleus for reasons unknown.
D) more stable than electrons farther from the nucleus.
E) Actually, electrons farther from the nucleus are filled first.