(3) Let $n$ be a positive integer, $x=\left(1+\frac{1}{n}\right)^{n}, y=\left(1+\frac{1}{n}\right)^{n+1}$, then ( ).
(A) $x^{y}>y^{x}$
(B) $x^{y}=y^{x}$
(C) $x^{y}<y^{x}$
(D) Any of the above is possible
(3) B Hint: Given $x=\frac{(n+1)^{n}}{n^{n}}, y=\frac{(n+1)^{n+1}}{n^{n+1}}$, taking the logarithm easily yields $x^{y}=y^{x}$.