You need to use the related knowledge of permutation and combination here. To put it simply, no matter how you go, you must take 12 step, of which 6 steps must be moved down and 6 steps will not be moved to the right, so the problem is transformed into choosing 6 steps down from 12 step (the remaining 6 steps will naturally turn to the right), depending on how many different selection methods are needed, that is, C (the right subscript is 65438+).

This is the content of elective course 2-3 in B version of senior high school mathematics teaching. You can check the corresponding counseling books.

Which of the following is A and B?