Final answer:
The correct option that results in a reduced molecule is loss of electrons (option C).
Step-by-step explanation:
Reduction is the process of gaining electrons or losing oxygen. Loss of phosphate (A) and gain of phosphate (B) do not involve gaining or losing electrons, so they do not result in a reduced molecule. On the other hand, loss of electrons (C) and gain of electrons (D) both involve the transfer of electrons, with loss of electrons resulting in a reduced molecule. Therefore, the correct answer is option C) loss of electrons.