Which of the following contains a vague pronoun reference?
A: After Tyler explained the chemistry homework to Bob, he understood it better, too.
B: After Tyler explained the chemistry homework to Bob, Tyler understood it better, too.
The second answer choice contains a vague pronoun reference. The pronoun he could refer to Tyler or Bob.
The first answer choice shows a possible correction for the vague pronoun reference. He has been replaced with Tyler.
After Tyler explained the chemistry homework to Bob, Tyler understood it better, too.