Identify the set comprising cold blooded organisms.

Animals are classified as cold-blooded (ectothermic/poikilothermic) or warm-blooded (endothermic/homeothermic) based on how they regulate body temperature. Cold-blooded animals cannot internally regulate their body temperature — it fluctuates with the surrounding environment; this group includes reptiles, amphibians, fish, and invertebrates such as insects and worms. Warm-blooded animals — birds and mammals — maintain a constant internal body temperature regardless of external conditions.

In the set Snake, Frog, Cockroach: the snake is a reptile, the frog is an amphibian, and the cockroach is an insect (an invertebrate) — all three groups are ectothermic, so every member of this set is cold-blooded.

• Lizard, Parrot, Dolphin — the parrot (a bird) and the dolphin (a mammal) are warm-blooded, so this set is not entirely cold-blooded.

• Pigeon, Humans, Lizard — the pigeon (a bird) and humans (mammals) are warm-blooded, so this set is not entirely cold-blooded.

• Whale, Frog, Earthworm — the whale is a mammal and therefore warm-blooded, so this set is not entirely cold-blooded.

Only the set of snake, frog, and cockroach consists entirely of cold-blooded organisms.