How many pairs of rational number (x,y) are there satisfying the equation y \equal{} \sqrt {x^{2} \plus{} \frac {1}{1999} }?<spanclass=′latex−bold′>(A)</span>0<spanclass=′latex−bold′>(B)</span>2<spanclass=′latex−bold′>(C)</span>3<spanclass=′latex−bold′>(D)</span>4<spanclass=′latex−bold′>(E)</span>Infinitely many