Final answer:
The statement that is not true about mammals is that they are cold-blooded animals. Mammals are actually warm-blooded, meaning they can maintain their internal body temperature regardless of the environmental conditions. Other true mammal characteristics include having hair, suckling their young, and birthing live young.
Step-by-step explanation:
The statement about mammals that is not true is option (c): 'they are cold-blooded animals'. In biological terms, mammals are warm-blooded, which means they have the ability to maintain a relatively stable internal body temperature regardless of the environmental conditions. This is also known as endothermy. Other characteristics of mammals include having hair on their skin, suckling their young ones, and giving birth to live young ones, not eggs.
Learn more about Mammal Characteristics