Context: Most mammals are viviparous, giving birth to live young. However, the five species of monotreme, the platypuses and the echidnas, lay eggs. The monotremes have a sex determination system different from that of most other mammals. In particular, the sex chromosomes of a platypus are more like those of a chicken than those of a therian mammal. Like marsupials and most other mammals, monotreme young are larval and fetus-like, as the presence of epipubic bones prevents the expansion of the torso, forcing them to produce small young.

Question: What is the common mammal group that gives birth to live young?
Answer: viviparous

Question: How many species of mammals lay eggs?
Answer: five species

Question: Which mammal that has the bill of a duck lays eggs?
Answer: platypus

Question: The platypus has sex chromosomes more related to which other non-mammal?
Answer: chicken

Question: What makes most monotreme viviparous?
Answer: Unanswerable

Question: What do marsupials have that is different from most mammals?
Answer: Unanswerable

Question: How many species of mammals give birth to live young?
Answer: Unanswerable

Question: What are some characteristics of young chickens?
Answer: Unanswerable

Question: What do marsupials have that make them less like a therian?
Answer: Unanswerable