What is the pronoun in sentence all of students know both?

The pronoun in the sentence "All of the students know both" is both.

Here's why:

* Pronouns stand in for nouns. In this sentence, "both" is replacing a noun phrase like "both of the teachers" or "both of the subjects."

* "All" is a quantifier, indicating the entirety of the students.

While "students" is a noun, it's not acting as a pronoun in this sentence.