Why do cells not have membrane transport proteins for O₂?

A) Because they need to keep the oxygen concentration low inside the reducing environment of the cell.
B) Because oxygen can dissolve in water and leak in via water channels.
C) Because oxygen can dissolve in the lipid bilayer and diffuse in and out rapidly without the need for a transporter.
D) Because oxygen is transported in and out of the cell in special oxygen-carrying proteins such as hemoglobin.
E) Because oxygen transport across a membrane is energetically unfavorable.