(2) Let $A_{k}=\left\{x \left\lvert\, x=k t+\frac{1}{k t}\right., \frac{1}{k^{2}} \leqslant t \leqslant 1\right\}(k=2,3, \cdots, 2012)$, then the intersection of all $A_{k}$ is ( ).
(A) $\varnothing$
(B) $\{2\}$
(C) $\left[2, \frac{5}{2}\right]$
(D) $\left[2, \frac{2012^{2}+1}{2012}\right]$
(2) $\mathrm{C}$ Hint: By the property of the "tick" function, $A_{k}=\left[2, k+\frac{1}{k}\right]$, and $k+\frac{1}{k}$ is increasing for $k \in [2,+\infty)$, thus the intersection of all $A_{k}$ is $A_{2}=\left[2, \frac{5}{2}\right]$.