C. the circumference is the answer
If we do not care about order, then a combination is an arrangement of r objects chosen from n distinct objects. It can often be seen written as:

or

Its factorial form is:
70/6 is basically saying "divide 70 by 6". So to get to a mixed numer, thats what you have to do.
70/6=11.666666...
(.666666..... is 2/3 as a fraction)
The answer is 11 2/3.
hope i helped!! :))