Multi choice chemistry question

Which of the following compounds of manganese can be reduced to form the other three?

A) MnO
B) MnO2
C) KMnO4
D) K2MnO4

Explain why

c) KMnO4

It is in the highest oxidation state for Mn, namely Mn(VII). Reducing involves lowering the oxidation state of an element by some chemical or physical means.

K2MnO4 is Mn(VI), MnO2 is Mn(IV) and MnO is Mn(II)