Which atom in the following reactions undergoes a change of oxidation

1.	Which atom in the following reactions undergoes a change of oxidation state of -5 ?
Answer» `MnO_(4)^(-)toMn^(2+)` `Cr_(2)O_(7)^(2-)to2Cr^(3+)` `MnO_(4)^(-)toMnO_(2)` `CrO_(4)^(2-)TOCR^(3+)` Answer :A

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