Cold-blooded animals, also known as ectothermic animals, are animals whose body temperature varies according to the temperature of their environment. This means that their body temperature is not regulated internally like warm-blooded animals. Instead, they rely on external sources of heat, such as the sun or warmer surroundings, to raise their body temperature. In contrast, warm-blooded animals, or endothermic animals, are able to regulate their body temperature internally, keeping it constant regardless of the external environment.

Option 1 is incorrect because cold-blooded animals can still have haemoglobin in their blood. Haemoglobin is the oxygen-carrying protein found in the red blood cells of animals.

Option 2 is incorrect because being cold-blooded has nothing to do with an animal`s temperament or behavior. It is solely related to their body temperature regulation.

Option 3 is also incorrect because the body temperature of cold-blooded animals does not remain constant. It fluctuates depending on the surrounding temperature.

Option 4 is the correct answer as it accurately describes the characteristic of cold-blooded animals in relation to their body temperature regulation. Alert - correct answer should be .