Oxidation reduction reactions oxidation reduction reactions may involve the loss of hydrogen and electrons are rarely coupled together utilize hydrogenases occur via the gain of hydrogen or the loss of oxygen

Oxidation-Reduction (REDOX) reactions can be defined with respect to electrons and Hydrogen and Oxygen.

Electrons:
                In a reaction the atom which looses electron(s) is said to be oxidized (reducing agent) and the atom which gains electron(s) is said to be reduced (oxidizing agent).

Oxygen-Hydrogen:
                            In a reaction if a reactant looses hydrogen or gain oxygen is said to be oxidized and the reactant which looses oxygen and gains hydrogen is said to be reduced.

Result:
           The correct answer is "May involve in loss of Hydrogen and Electrons".