You need to be more careful with parentheses. You have technically written x+(y/x), but I think you meant (x+y)/x. They are vastly different!
Try breaking the fraction apart and see where that leads.
If 0<x<y and x/y=r, which of the following must be equal to x+y/x?
The answer is r+1/r (D).
I don't understand how they did this.
I'm thinking it's because since x/y=r, if we moved the y over to the right, it'd be x=ry. So, in assuming that somehow y=1, then r multiplied by 1 would be r, thus x=r. And if x=r, then r would replace x in the fraction and 1 would replace y. But that doesn't make sense because why would y = 1? help. :P