Which of the statements below is valid?

The statement that is valid is "The body temperature of the bird remained constant despite changes in environmental temperature." Birds are endothermic animals, which means that they can regulate their body temperature internally, independent of the environmental temperature. They maintain a constant body temperature through various physiological mechanisms, such as shivering, panting, and fluffing their feathers. In contrast, lizards are ectothermic animals, which means that they rely on the environmental temperature to regulate their body temperature. Their body temperature is usually close to that of the environmental temperature, and it can vary significantly depending on the ambient conditions. Therefore, the statement that "The body temperature of the bird remained constant despite changes in environmental temperature" is the only correct statement as it describes the ability of birds to maintain a constant body temperature, regardless of changes in the environmental temperature.