External Gills, Tracheae, and Lungs Share Which of the Following

External gills, tracheae, and lungs share which of the following sets of characteristics?

A) They are parts of gas-exchange systems, they exchange both CO₂ and O₂, and they increase surface area for diffusion.
B) They are used by water breathers, their functioning is based on countercurrent exchange, and they make use of negative pressure for breathing.
C) They exchange only O₂, they are associated with a circulatory system, and they are found in vertebrates.
D) They are found in insects, they employ positive-pressure pumping, and their functioning is based on crosscurrent flow.
E) They are parts of gas-exchange systems, they ex­change both CO₂ and O₂, and they decrease surface area for diffusion.