What mechanism do animals use to navigate their environment in response to a stimulus?

The correct choice of mechanism that animals use to navigate their environment in response to a stimulus is taxis. Taxis refers to the directed movement of an organism toward or away from a stimulus, often involving specific environmental cues such as light, smell, or temperature. For example, a common type of taxis is phototaxis, where an organism moves toward light sources, which can be critical for survival, aiding in finding food or avoiding predators.

On the other hand, homeostasis represents an organism's ability to maintain internal balance despite changes in the external environment, but it does not specifically involve navigation or movement in response to environmental stimuli. Chromotropism is related to plant responses, particularly in how plants grow towards or away from a certain color of light, which is not applicable to animal navigation. Complex behavior encompasses a broader range of actions and responses that are learned and can involve a sequence of behaviors, but it does not specifically denote the immediate and directional movement seen in taxis.