Which of the following reactions are disproportionation reaction ?

Question : Which of the following reactions are disproportionation reaction ?

(I) \text {Cu}^{+}\rightarrow \text {Cu}^{2+}+\text {Cu}

(II) \text {3MnO}_{4}^{-}+\text {4H}^{+}\rightarrow \text {2MnO}_{4}^{-}+\text {MnO}_{2}+\text {2H}_{2}\text {O}

(III) \text {2KMnO}_{4}\rightarrow \text {K}_{2}\text {MnO}_{4}+\text {MnO}_{2}+\text {O}_{2}

(IV) \text {2MnO}_{4}^{-}+\text {3Mn}^{+2}+\text {2H}_{2}\text {O}\rightarrow \text {5MnO}_{2}+\text {4H}^{+}

Select the correct option from the following

(1) (I) and (II) only (2) (I), (II) and (III)
(3) (I), (III) and (IV) (4) (I) and (IV) only
answer : from all above options the correct answer is “(I) \text {Cu}^{+}\rightarrow \text {Cu}^{2+}+\text {Cu}
explanation of correct answer : Disproportionation reactions are those reactions which show redox reactions , it means in these type of reaction oxidation and reduction both reactions took place together or we can say simultaneously.
Disproportionation reactions are also called redox reactions in which an element in a compound is simultaneously or together oxidized as well as reduced.

2Cu+  → Cu2+ + Cu

+1    →  +2     0

3MnO42-  + 4H+ → 2MnO4 + MnO2 + 2H2O

+6                      →  +7            +4

that is why the correct answer is “(I) \text {Cu}^{+}\rightarrow \text {Cu}^{2+}+\text {Cu}