Which of the following animals does not use the trachea as the respiratory organ? 

Prawn does not use the trachea as the respiratory organ. They are aquatic animals and have gills for the respiration process.

Insects have a tracheal respiratory system in which oxygen and carbon dioxide travel primarily through air-filled tubes called tracheae. For example, grasshoppers, mosquitoes, cockroaches etc., possess a tracheal respiratory system.

Usually, the tracheal system penetrates the cuticle via closeable valves called spiracles and ends near or within the tissues in tiny tubes called tracheoles.