It's a bit of a bummer to have to work through all of these to find the answer. That a lot of slope calculations (or graphing, or whatever). When there are this many, a spreadsheet or other machine help can make it easier.
The correct choice is the last one, XYZ, with vertex X being where the right angle is located.
_____ Slope of XY is 4/7; slope of XZ is -7/4. The product of these is -1, so those segments are at right angles.
