Need one final boost? This South Dakota CDL Combination Vehicles Marathon is a monster of a study tool that contains a combination of all 99 questions that we have available for this SD endorsement. If you make a mistake, we’ll remember that question and will display it to you again at the very end of the Marathon until you’ve answered that question correctly. In other words, the Marathon will cycle through your missed questions until you answer each one correctly. You must make a 100% to pass. We suggest you attempt this one after you have practiced the state’s “regular” tests, but before the “Exam”. Give it your best shot!