The outer shell electronic configuration of Gd (Z = 64) is

Options

A. `[Xe] 4f^6 5d^1 6s^2, [Xe] 4f^7 5d^1 6s^2` and `[Xe] 4f^8 5d^1 6s^2`
B. `[Xe] 4f^7 6s^2, [Xe] 4f^7 5d^1 6s^2` and `[Xe] 4f^9 6s^2`
C. `[Xe] 4f^7 6s^2, [Xe] 4f^8 5d^1 6s^2` and `[Xe] 4f^8 5d^1 6s^2`
D. `[Xe] 4f^6 5d^1 6s^2, [Xe] 4f^7 5d^1 6s^2` and `[Xe] 4f^9 6s^2`