Threatening behavior by predators causes a porcupine to extend its quills.
Porcupine quills can be extraordinarily painful.
Threatening behavior towards porcupine by predators can cause the predator pain.
What can cause predators pain?
[A] animals with backbones
[B] Staying away from porcupine
[C] Ignoring porcupine
[D] pressure on the skin
[E] Befriending porcupine
[F] Threatening behavior towards porcupine
[G] Something with a head, thorax, and abdomen
[H] the body's largest organ