In the electron transport system during tissue respiration,the role of cytochrome oxidase is

• A
  As the final acceptor of $2$ electrons which activate ${O_2}$ to form $CO_2$
• B
  In accepting $2$ electrons to be transported to the other cytochromes
• C
  As final acceptor of $2$ electrons to form water
• D
  As final acceptor of an electron to form water