Which of the following contains a vague pronoun reference?

 - Brad felt better about collaborating on the research project after Eric talked with him about it.
 - After Eric talked with Brad about the research project, he felt better about collaborating on it.
The first answer choice contains a vague pronoun reference. The pronoun he could refer to Eric or Brad.
After Eric talked with Brad about the research project, he felt better about collaborating on it.
The second answer choice shows a possible correction for the vague pronoun reference. The text has been rewritten so that the meaning is clear.
Brad felt better about collaborating on the research project after Eric talked with him about it.