Which of the following contains a vague pronoun reference?

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