What is the sequence to label the subshells in an atom?

Q. What is the sequence to label the subshells in an atom?

A.            S, p, d, f, g

B.            S, p, p, f, d

C.            S, s, p, p, d, f, g

D.            S, p, g, d, f

Answer: S, p, d, f, g