The correct answer is option 3, Snake. Cold-blooded animals, also known as ectothermic animals, are unable to regulate their body temperature internally. Instead, they rely on external sources of heat to warm their bodies. Snakes fall into this category as they cannot generate their body heat. Instead, they bask in the sun to warm up and hide in cool areas to cool down.

Option 1, Ape, is incorrect because apes are warm-blooded animals, meaning they can regulate their body temperature internally.

Option 2, Mouse, is incorrect because mice are also warm-blooded animals.

Option 4, Wolf, is also incorrect because wolves are warm-blooded animals too.

Therefore, the correct answer is option 3, Snake, which is a cold-blooded animal.