What part of speech is the word that as in dog lives at ranch?

In the sentence "Dog lives at ranch," the word "that" is not present.

Let's analyze the sentence:

* Dog: Noun (subject of the sentence)

* lives: Verb (present tense)

* at: Preposition

* ranch: Noun (object of the preposition)

If you were to add "that" to the sentence, it would be used as a demonstrative pronoun to point out a specific dog.

For example:

* That dog lives at the ranch.

In this case, "that" is used to identify a specific dog, likely one that the speaker and listener are both aware of.