Consider the following statements regarding oxidation :
I. There is loss of hydrogen.
II. There is gain of oxygen.
III. There is gain of electrons.
IV. Oxidation state increases.
Which of the statements given above are correct?

Oxidation is defined through several chemical concepts:

• Classical Concept: Oxidation involves the addition of oxygen (or an electronegative element) or the removal of hydrogen (or an electropositive element). Thus, statements I and II are correct.
• Electronic Concept: Oxidation is the loss of electrons by an atom, ion, or molecule (often remembered by the mnemonic OIL RIG: Oxidation Is Loss, Reduction Is Gain). Statement III is incorrect as the gain of electrons is reduction.
• Oxidation Number: Since oxidation involves the loss of negatively charged electrons, the oxidation state (or number) increases (becomes more positive). Thus, statement IV is correct.

Since statements I, II, and IV are accurate descriptions of oxidation, the correct option is C.