Given a scientific passage and an answer, generate a question for the given answer.

[Q]: Passage: The embryo develops from a fertilized egg. While still inside the seed, the embryo forms its first leaf (cotyledon) and starts to develop a stem (hypocotyl) and root (radicle). Answer: cotyledon
[A]: What is the name of the first leaf developed inside an embryo?

[Q]: Passage: Momentum is a vector quantity that has the same direction as the velocity of the object. Answer: object ' s velocity
[A]: Momentum is a vector quantity that has the same direction as what?

[Q]: Passage: Not really. Like all mammals, polar bears maintain a stable internal temperature. They do not need to stay warm by lying in the sun. This allows them to live in cold climates. Answer: mammals
[A]:
The ability to maintain a stable internal temperature, despite the climate, is exhibited by members of what animal group?