Final answer:
The vague pronoun in the sentence is 'they'. To make the meaning clear, the sentence can be rewritten as follows: 'The teachers told the students that the teachers were going on a field trip.'
Step-by-step explanation:
Vague pronouns occur when the antecedent (the noun to which the pronoun refers) is unclear or ambiguous. This lack of clarity can lead to confusion and make it difficult for the reader or listener to understand the intended meaning. To avoid vague pronouns, it's important to ensure that the antecedent is clearly identified.
The vague pronoun in the sentence is 'they'.
To make the meaning clear, the sentence can be rewritten as follows: 'The teachers told the students that the teachers were going on a field trip.'