What is an appropriate example of a pronoun?

A pronoun is a word that takes the place of a noun in order to avoid repetition and make sentences clearer and more concise. The word "they" serves this function perfectly, as it can refer back to a previously mentioned group of people or things without needing to repeat the noun itself. For instance, instead of saying "The students went to the game, and the students enjoyed it," you can simply say, "The students went to the game, and they enjoyed it."

In contrast, the other options represent different parts of speech. "Running" is a verb or gerund; "green" is an adjective describing color; and "and" is a conjunction used to connect words, phrases, or clauses. These words do not fulfill the role of pronouns, which is specifically to substitute for nouns.