An animal needs to attract a mate to reproduce.
Mammals are animals which raise their young on milk and typically give birth to live young.
A mammal needs to attract a mate to give birth to live young.
What needs to attract a mate in order to give birth to live young?

1: humans
2: Jellyfish
3: mammals
4: Frogs
5: birds
6: hormones
7: insects
8: reptiles