c) Art Mokarow
Well, Paul has seven uncontested letters, the Johannine corpus is a bit of a mess (is John the Elder the same as John the Disciple, and what about John of Patmos?) but given the most generous estimate it can't go beyond five. Solomon was credited with Proverbs and Ecclesiastes, but even if that was so (and it isn't) it counts as only two. Moses has four to his credit, if you discount the efforts of JEP and D...
But Art Mokarow is clearly the winner, and here's proof from an ad appearing on Alan Ruth's Journal website (Alan is webmaster, and seems to be contracted to handle its day to day running.)
Order Free CD that unlocks the Bible's Mysteries
by Art Mokarow, author of 12 Biblical books!