Which Statement About the Respiratory System of Air-Breathing Insects Is

Which statement about the respiratory system of air-breathing insects is true?

A) Respiratory gases diffuse through fluid most of the way to and from cells.
B) Spiracles are gated openings restricted to the thorax region.
C) Spiracles are permanently open.
D) Air sacs are gas exchange surfaces.
E) Spiracles open to allow gas exchange.