3. Let $a, b$ be any distinct positive numbers, and $x=\frac{b^{2}+1}{a}, y=\frac{a^{2}+1}{b}$. Then $x, y$ must ( ).
(A) both not be greater than 2
(B) both not be less than 2
(C) at least one is greater than 2
(D) at least one is less than 2
3. (C).

Let $a=1, b=3$, then $x=10, y=\frac{2}{3}$. This negates (A) and (B). Let $a=3, b=4$, then $x=\frac{17}{3}, y=\frac{10}{4}$. This negates (D), hence only (C) is correct.