Which of the Following Statements Is/are Correct

Multiple Choice

Which of the following statements is/are correct?
i.Principal energy levels are identified by the letters s,p,d,and f
ii.Principal energy levels appear in both the quantum mechanical model of the atom and the Bohr model of the atom
iii.In general,n = 1 is at lower energy than n = 2,and n = 2 is lower than n = 3,and so on
iv.The principal energy level is related to electron spin

A) i only
B) iv only
C) i and ii
D) ii and iii
E) iii and iv