Final answer:
Francis P. Church's published response to Virginia's letter about Santa Claus is classified as an editorial because it expresses an opinion on the issue of belief and skepticism.
Step-by-step explanation:
The type of published response written by Francis P. Church to Virginia's letter is an editorial. Editorials are articles in a newspaper or other periodical presenting the opinion of the publisher, editor, or editors. They are designed to persuade readers to think a certain way about a topic, and in this case, Church is discussing the existence of Santa Claus and the broader implications of belief and skepticism. An editorial is associated with the commentary or expression of an opinion on a topical issue, rather than a purely informational piece like a feature article or an objective reporting like an essay. Since Church's response takes a stance and provides commentary, this best fits the description of an editorial.