instruction: What qualifies an animal as a monotreme?
response: A monotreme is a mammal that lays eggs.  This is uncommon as there are only two mammals, the echidnas and platypus, that do so.  The majority of mammals give placenta birth, with another minority of mammals, known as marsupials, give birth to a fetus-like embryo which is dependent of mother's teat to provide nourishment until fully developed.