单选题(4.0分)-|||-16. lim _(xarrow infty )dfrac (xsqrt {{x)^2+(y)^2}}({x)^2+y}= ()-|||-A dfrac (sqrt {5)}(3)-|||-B dfrac (3sqrt {5)}(5)-|||-C 极限不存在-|||-D dfrac (sqrt {5)}(5)