Possible Values of the Principal Quantum Number N for an Electron

Multiple Choice

Possible values of the principal quantum number n for an electron in an atom are:

A) only 0 and 1
B) only 0,1,2,..., $\infty$
C) only 0,1,..., -1
D) only 1/2 and -1/2
E) only 1,2,3,..., $\infty$