Let $f(x) = \lim_{n}$ ${\rightarrow \infty} \left( \frac{n^n(x+n)(x+\frac{n}{2}) \cdots (x+\frac{n}{n})}{n!(x^2+n^2)(x^2+\frac{n^2}{4}) \cdots (x^2+\frac{n^2}{n^2})} \right)^{\frac{x}{n}}$,for all $x > 0$. Then
$(A)$ $f(\frac{1}{2}) \geq f(1)$
$(B)$ $f(\frac{1}{3}) \leq f(\frac{2}{3})$
$(C)$ $f^{\prime}(2) \leq 0$
$(D)$ $\frac{f^{\prime}(3)}{f(3)} \geq \frac{f^{\prime}(2)}{f(2)}$

• A
  $B, C$
• B
  $B, D$
• C
  $A, B$
• D
  $A, C$