The derivative of \( \left| \frac{x}{4} \right| \) is evaluated by first considering the absolute value function. We know that:
\[
\frac{d}{dx} \left| x \right| = \frac{x}{|x|}.
\]
Thus, for \( \left| \frac{x}{4} \right| \), the derivative is:
\[
\frac{d}{dx} \left[ \left| \frac{x}{4} \right| \right] = \frac{1}{4}.
\]
Therefore, the correct answer is option (B) 4.