Which of the following is a proximate question in regards to animal behavior?

A) Why do parents risk their lives for those of their offspring?
B) Why do crows work together to attack great horned owls?
C) Why does a gazelle leap to warn others in the herd when a predator is present?
D) How does a male songbird learn the songs that attract females of his species?
E) When does a human male develop a deep voice?