单项选择题
A.Twain was successful in writing at last. B.Twain was a famous humorist. C.Twain's writing style was easy to be understood. D.Twain wrote many poems about Mississipp
A.It came from a safe passage. B.It came from a term used by the boatmen. C.It came from his boyhood. D.It came from his measuring tool.
A.Asia B.the United States C.Europe D.Both B and C