Objectivity is blank and white. In other words, it is right or wrong. So, which answer shows he is not trying to guess or be wishy-washy? Pathos is trying to appeal to one's emotions. So, he is trying to say that he will never forget how happy he was allowed to go live with another in order to become educated. When you look at the given answers, it can't be C as he was not happy to see Thomas but to receive the education. It can't be D because there is not explanation about the relationship. I do believe A is your best answer.
I think the answer is that Sarah should look up words she doesn't know for chapter titles, headings and first paragraphs and write the main idea in her own words.