Which of the following contains a vague pronoun reference?

 - Mrs. Monroe told her assistant to book a flight to Springtown immediately.
 - Mrs. Monroe informed her assistant that she had to book a flight to Seoul immediately.
The second answer choice contains a vague pronoun reference. The pronoun she could refer to Mrs. Monroe or her assistant.
Mrs. Monroe informed her assistant that she had to book a flight to Seoul immediately.
The first answer choice shows a possible correction for the vague pronoun reference. The text has been rewritten so that the meaning is clear.
Mrs. Monroe told her assistant to book a flight to Springtown immediately.