Given a scientific question and its correct answer, generate supporting facts for the answer. This supporting fact can be an explanation for the answer to the given question.

Question: What types of glands do only female mammals have? Answer: mammary
Two traits are used to define the mammal class. They are fur or hair and mammary glands in females.

Question: Nonvascular plants lack vascular tissue and what? Answer: seeds
Nonvascular plants lack seeds and vascular tissue.

Question: Momentum is a vector quantity that has the same direction as what? Answer: object ' s velocity
Momentum is a vector quantity that has the same direction as the velocity of the object.