Step-by-step explanation:
It's none of these.
Cr- 1s2 2s2 2p6 3s2 3p6 4s1 3d5
Mg- 1s2 2s2 2p6 3s2
Mn - 1s2 2s2 2p6 3s2 3p6 4s2 3d5
Fe- 1s2 2s2 2p6 3s2 3p6 4s2 3d6
I think there's a mistake in the question.
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