Biological oxidation-reduction reactions always involve:

a. direct participation of oxygen.

b. transfer of electron (s).

c. mitochondria.

d. transfer of hydrogens.

e. formation of water.

b. transfer of electron (s).

Explanation:

An oxidation-reduction also called a redox reaction is a

chemical reaction in which electrons are transferred of between two species of reactants. It is a chemical reaction where the oxidation number of an atom, ion, or molecule, increases or decreases by losing or gaining electrons