Critics of the Book of Mormon note the fact that the title "Christ" was on the small plates (see 2 Nephi 10:3); but then in the book of Mosiah, Benjamin reports learning the name of Christ through a revelation from an angel (see Mosiah 3:2, 8). The critics then raise a valid question: "Why would king Benjamin have to receive a special revelation informing him of the name of Christ if the plates of Nephi already contained this information?"
According to Ara Norwood, the answer can be found by careful study of both passages. In the case of Benjamin, we find that a great deal more than the name of Christ is revealed. For instance, in Mosiah 3, we discover that Benjamin learned many things from the angel concerning the ministry of Jesus that he could not have learned from the revelation Jacob recorded in 2 Nephi 10. In fact, from the perspective alone of what was written of both revelations, the majority of the revelation to Benjamin is actually unique. But even if it were not, Benjamin, as an independent witness, had every reason to record his sacred experience--just as the various gospel writers in the New Testament had every reason to record their overlapping testimonies of the life of Christ.
Concerning Benjamin's use of the name "Jesus Christ, the Son of God" during the supposed pre-Christian era, they simply represent his best effort to express in the translator Joseph Smith's language (i.e., nineteenth-century American English) the meaning of the words revealed by God. It should be clear that any rendering of words or ideas from ancient times into a modern language must necessarily use words that would have been unavailable anciently. This is as true of a modern translation of Cicero, Aescylus, or Confucius as it is of Joseph Smith's translation of the Book of Mormon. [L. Ara Norwood, "Book Review of Jerald and Sandra Tanner's, Covering Up the Black Hole in the Book of Mormon, in Review of Books on the Book of Mormon, Vol. 3 1991, pp. 164-165]
Note* As for someone having a designated name that was apparently known beforehand, critics of the Book of Mormon should note that John the Baptist's name was specifically given to Zacharias (see Luke 1:13). If a name was specifically given by an angel from God beforehand, then the name of John was apparently planned and known from the beginning. [Alan C. Miner, Personal Notes]