The sentence that has an indefinite-pronoun verb agreement error is sentence 4. Indefinite pronouns used as subjects must agree with the verbs. In sentence 4, the indefinite pronoun<em> "each" </em>is used as subject and it is singular while the verb <em>"teach"</em> is in plural form. This is why there is an error in agreement. The solution would be the following: <em>"Each of the teachers teaches in a different way."</em>
