Travel Information about France and Paris

(GMT)13 JAN 2017 USLEO94:  I have heard that Mont st Michel is good for a day trip from Paris. It is a UNESCO World Heritage site.
What would be the best transportation option to get from Paris to Mont st Michel and back to Paris?

(GMT)14 JAN 2017 TRAVELINTER TEAM:  Hi, refer to the following info.
1. Paris Montparnasse ->Rennes by high-speed train(takes 2h 05), then the express Keolis Emeraude bus to Mont St Michel.
2. Paris Montparnasse -> Dol de Bretagne then take a bus)to > Mont St Michel.
At Paris Gare Montparnasse you can purchased a train ticket that included a bus transfer to Mont St Michel.