Answer:
An article about Kennedy written by a professional historian
Step-by-step explanation:
An informative essay is a type of essay that aims to educate its readers on a certain topic.
When writing an informative essay, it's important that we use only correct information. This is why a person writing about John F. Kennedy should use an article about Kennedy written by a professional historian as a source. It's guaranteed that this type of article will include only facts.
However, there is no guarantee that a student's report about Kennedy would be correct. Both the memoir written by Kennedy's wife and a book titled Why John F. Kennedy Was America's Greatest President lack objectivity. They are influenced by their writers' opinions, beliefs, and feelings, which means that they are not based on facts.
This is why the third option is the correct one.