B. A type of church music sung primarily by African Americans and white Southerners
C. a shorthand way of explaining how to become a Christian or "get saved"
D. a euphemism for any true statement
E. None of the Above
If "gospel" is used to describe too many things, it becomes somewhat meaningless, almost like our culture's "4 letter words." If we look at the Bible (this should make sense as a starting place) we see that "gospel" or "good news" is part of the message of Isaiah in the Hebrew scriptures (Hebrew - besara) and it is the English translation in the New Testament of the Greek word evangelion presumably used by Jesus and Paul (unless you believe in Aramaic priority but let's not go there). god-spell is not just a Broadway musical, it is the old English word meaning "good tidings/news" which is exactly what evangelion means. If you look close you can see the word "angel" there in the middle. Angels are so-called because they are the messengers of God's news/tidings... You get it.
If, as Karl Barth suggests, the Christian "proclamation" (ie. basic message) is the foundation of Christian theology, then it might be important to figure out what that is. In addition to "None of the above" answers to our question, we'd have to add that "THE gospel" can't be both a summary of MY theology and also the foundation of CHRISTIAN theology (if my theology is Christian). Instead, we should hope that "THE gospel" creates the questions that any Christian theology tries to answer and we should try to figure out how the Bible (which gives us numerous examples of the message of Jesus and his earliest followers) uses the term "gospel" and derive our account of what "THE gospel" is from there.
For fun, let's insert Rob Bell's brief account of the gospel here, because Rob is a lightening rod for controversy (personally, I like him) and I might get more readers if I include it: