Which of the following is true regarding some insect tracheal systems?  

A) They are associated with the blood circulatory system.
B) They excrete body wastes as well as transport gases.
C) Their spiracles function like stomata in plants, opening for gas exchange and closing to conserve water.
D) The tracheal tubes are continually open in large terrestrial insects.
E) They contain respiratory pigments to enhance oxygen transport.