which electronic configuration is not observing

Question

Which electronic configuration is not observing the ( n+ 1) rule:

(1) 1s², 2s², 2p⁶, 3s², 3p⁶, 3d¹, 4s²              

(2) 1s^2, sp², sp⁶, 3s², 3p⁶, 3d⁷, 4s²       

(3) 1s^2, 2s², 2p⁶, 3s², 3p⁶, 3d⁵, 4s¹          

(4) 1s², 2s^2, 2p⁶, 3s^2, 3p⁶, 3d⁸, 4s²

Ans: 1s², 2s², 2p⁶, 3s², 3p⁶, 3d⁵, 4s¹