Answer the following question given this paragraph: 

Like many other animals, sheep travel in herds. The tendency is for each individual sheep to stay with the herd. However, a sheep may sometimes wander off, depending on how strong the attraction is for a particular food or water supply. At other times, a sheep may become frightened and run off. Whether a sheep chooses to stay with the herd or go its own way depends on the balance between attraction to the herd and attraction to the outside influence.


Q: What is the collective travel of sheep known as?

 Choices:

- gaggle

- load

- den

- herd

A:
herd
