Concept:Fish are cold-blooded (poikilothermic) vertebrates, not warm-blooded (homeothermic).Explanation:Fish use gills for respiration.Most fish are covered with scales.Fish do not maintain a constant internal body temperature, so they are poikilothermic, not homeothermic.Therefore, the statement “they are homeothermic” is not true of a fish.Answer:C. they are homeothermic