question_answer

What must be added to \[\frac{x}{y}\] make it\[\frac{y}{x}\] ?

A)  \[\frac{y-x}{{{y}^{2}}{{x}^{2}}}\]             

B)        \[\frac{{{y}^{2}}-{{x}^{2}}}{yx}\]  

C) \[\frac{xy}{x+y}\]           

D)        \[\frac{{{x}^{2}}{{y}^{2}}}{{{x}^{2}}+{{y}^{2}}}\]