Which of the following reactions involves neither oxidation nor reduction ?

Options

A. `CrO_(4)^(2-) to Cr_(2)O_(7)^(2-)`
B. `Cr to CrCl_(3)`
C. `Na rarr Na^(+)`
D. `2S_(2)O_(3)^(2-) to S_(4)O_(6)^(2-)`

Answer

A

Explanation

`overset(+6""+2)(C"r"O_(4)^(2)) to overset(+6)(Cr_(2))overset(-2)(O_(7)^(2-))`
`therefore` O.N. of Cr does not change.