The reasonable ground-state electron configuration among the options provided is 1s²2s²2p⁶3s²3p⁶4s²3d⁵. This configuration corresponds to manganese (atomic number 25) and reflects the correct filling order of orbitals according to the Aufbau principle, Hund's rule, and the Pauli exclusion principle. The other configurations either exceed the allowed number of electrons in certain orbitals or are not in the correct order of filling.