Which of the following are characteristics of reptiles?

Reptiles are indeed characterized by being cold-blooded, which means their body temperature is regulated by their environment rather than internal mechanisms like those of warm-blooded animals. Additionally, laying eggs is a typical reproductive method for many reptiles, although some species give birth to live young. These traits are fundamental to the classification of reptiles within the animal kingdom, setting them apart from birds and mammals, which have different physiological and reproductive characteristics.

Other choices describe characteristics specific to various groups of animals. For example, warm-blooded and mammary glands refer to mammals, while breathing in water and having fins pertain to aquatic animals like fish. Hollow bones and the ability to fly are features associated with birds, not reptiles. Understanding these distinctions is crucial for recognizing the biological classifications and adaptations inherent to different animal groups.