The background of the missionaries in these chapters is not explicitly explained. Instead, it can be inferred based on parallel plot. A parallel plot is a one more story line that seem to have nothing in common with the lead story line, but it is usually contains additional information or background of an event or a character which makes a story be more deep.
The correct answer is C. He opened the field of literary criticism.
Apart from being a poet and a writer during the Romantic era of American literature, Edgar Allan Poe was also a critic. As a matter of fact, while he was alive, he wasn't really famous or celebrated as an author, but rather as a critic. Only after his death did people start appreciating his art, but it was too late - he died poor.