Which expression is equivalent to the following complex fraction? startfraction 1 over x endfraction minus startfraction 1 over y endfraction divided by startfraction 1 over x endfraction startfraction 1 over y endfraction a. startfraction y x over y minus x endfraction b. startfraction (y minus x) (y x) over x squared y squared endfraction c. startfraction x squared y squared over (y x) (y x) endfraction d. startfraction y minus x over y x endfraction