What action is associated with the sound that sheep make?

The action associated with the sound that sheep make is described by the term "bleat." Sheep use this vocalization primarily as a means of communication, expressing various emotions or needs such as hunger, distress, or social interaction with their flock. Each animal species has its unique sounds, and in the case of sheep, "bleating" is specifically recognized and commonly understood as their characteristic sound.

In the context of the other choices, while "ruminate" relates to cattle's digestive process, "gnaw" refers to rats' action of chewing persistently, and "gallop" describes the fast movement of horses. These actions represent different behaviors of the respective animals but do not define the specific sounds they make. The sound that sheep produce is a distinct trait of their nature, emphasizing the connection between the animal and its vocalization. Thus, "bleat" is the correct answer, accurately reflecting the sound characteristic of sheep.