What does it mean when asked what is the source that you are going to research

Choose the sentence that is not logically connected in the paragraph. (1) doctor henderson was a kind and gentle man. (2) his patients loved and respected him. his death made many of them sad. (3) as a young man, he decided to become a doctor and pursue a life of healing and comforting. (4) his work will long be remembered by the citizens of battle creek, michigan.