Explanation

To find the median, first, we need to arrange the numbers in ascending order:

1, 5, 5, 5, 7, 8, 8, 9, 9, 10, 10

There are 11 numbers in total. Since there is an odd number of values, the median will be the middle number, which is 8.

However, if you're asking about the given options (5, 7, 8, 9), they are actually the values less than or equal to the median, not the median itself. So, the correct explanation would be:

The median of the given set is 8 because when arranged in ascending order, the middle value is 8.