In oxidative photophosphorylation,the last $3$ steps are as follows: $Q \to C \to aa_3 \to O_2$. Which of the following statements is correct regarding the proton $(H^+)$ movement?

• A
  $Q \to C$ is an $H^+$ absorbing site.
• B
  $aa_3 \to O_2$ is an $H^+$ yielding site.
• C
  $Q \to C$ is an $H^+$ yielding site and $aa_3 \to O_2$ is an $H^+$ absorbing site.
• D
  No $H^+$ is absorbed or released during these steps.