Which sentence avoids using a pronoun reference error? Which sentence avoids using a pronoun reference error?

Al had a dog with fleas, which he was always scratching.
When I called the college, they said they were still accepting applications.
When Kara went to help her sister fix supper, she was very angry.
none of the above

The sentence that avoids using a pronoun reference error is James wants to study medicine because his brother is a doctor. In this sentence it is the most clear that the pronoun his refers to the subject James

hooch has about 3% alcohol content so the 5 gallon 90% platinum vodka would be stronger because it has a higher alcohol content then hooch.  

b.science

explanation: