Which of the following sums would be under the radical symbol to find the distance between the points (7, -1) and (-8, -9)?

Sadly, you didn't put any sums on your list of choices. 
In fact, I can't even find a list of choices !

To find the distance between  (7, -1)  and  (-8, -9),
you would build a sum under a square-root (radical)
symbol, and it would look something like this:

               √ ( 225 + 64 ) .