Concept:Insects breathe through a network of air-filled tubes called tracheae.
Explanation:Oxygen enters the insect body through small openings called spiracles.
From the spiracles, air moves into the tracheae, which branch throughout the body.
The tracheae deliver oxygen directly to the tissues and carry carbon dioxide away.
The skin is not the main respiratory surface in insects.
Malpighian tubules are excretory structures, not respiratory structures.
Flame cells perform excretion in flatworms, not gas exchange in insects.
Answer:B. tracheae