Only the Catholic Church traces its lineage back to Christ. ALL christian churches are offshoots of the Catholic Church. The Mormon Church is not even christian. Gordon B. Hinckley, the current president and prophet of the Mormon church, says (in a booklet called What of the Mormons?) that he and his co-religionists "are no closer to Protestantism than they are to Catholicism."
You are dodging the question. Why is the Catholic churches claim to Apostolic succession more valid than the Morman's?