Where does oxidation occur in the electrochemical cell?
in the voltmeter
in the salt bridge
on the zinc electrode
on the copper electrode

The oxidation occur on the zinc electrode.

Explanation:

An electrochemical cell is a device in which chemical energy produced during reaction is converted into electrical energy. in these type of cells oxidation occurs at anode and reduction occurs at cathode.

At cathode :(reduction)

At anode: (oxidation)

the volume increases