An animal that hides under a rock to avoid predators is responding an?

An animal that hides under a rock to avoid predators is responding to a stimulus.

Here's why:

* Stimulus: A stimulus is anything in the environment that causes a reaction in an organism. In this case, the sight or sound of a predator is the stimulus.

* Response: The animal's action of hiding under a rock is its response to the stimulus.

This is a classic example of a reflex, an automatic response to a stimulus.