unimodel: A unimodal distribution is a distribution with one clear peak or most frequent value. The values increase at first, rising to a single peak where they then decrease.
A, C, and D can be a possibility but they are not exactly at the middle. B is the only one that shows a slightly triangular shape, which you can see the middle that shows the best measure of the center.
You first multiply 6 and 8 to see how many people are put in the vans without rented a van. This would equal 48. You then subtract 48 from 59 to see how many people still need to be in a van. This would leave you with 11 people. Then you divide 8 from 11 to get 1 3/8. This means you need 2 vans to fit everyone.