I would think that it is B. because it makes the most sense to me. it also could be B. for one other reason and that is converting helps to understand how to salve it on pencil and paper if you know how to convert on paper so my answer would be B.
If each member sells the same number of raffle tickets, then 13r would show that each of the 13 members will have sold <em>r</em> raffle tickets each. The expression is multiplication.