Which of the following contains a vague pronoun reference?

 - After Dan graduates, he plans to travel around Europe with his brother.
 - Dan plans to travel around Europe with his brother after he graduates.
The second answer choice contains a vague pronoun reference. The pronoun he could refer to Dan or his brother.
Dan plans to travel around Europe with his brother after he graduates.
The first answer choice shows a possible correction for the vague pronoun reference. The text has been rewritten so that the meaning is clear.
After Dan graduates, he plans to travel around Europe with his brother.