Answer:
Cu²+ e ----> Cu+
This is not oxidation as it gain electron .
Oxidation reaction means addition of oxygen or removal of hydrogen
or in other words loss of electrons
Mg ----> Mg²+ + 2e
this is oxidation reaction as Mg loss 2e to become +2
Sn³+ -----> Sn4+ + 2e
this is oxidation reaction as it losses electrons
similarly other are also oxidation.
