Summer said that it didn’t matter which sides of a right triangle were a, b, and c. is she correct? a. yes, she is correct. b. no, a must be the shortest side, then b, and c is the longest side. c. no, c must be the shortest side, then b, and a is the longest side. d. no, a and b are interchangable, and c is the longest side.

It doesn't matter what you call the sides of your triangle. 
You could call them Ralph, Richard, and Marsha if you want to. 
But you MUST add enough information to everything you write
about that triangle that makes it clear what the names mean. 
A drawing, with labels on the sides and angles, is always a good idea.

When people are working with right triangles, the hypotenuse
(the longest side) is most often labeled 'c'.  But there's no law.
I'll gladly debate it with anyone who says there is.