Study the problem figures marked I, II, III and IV carefully to establish the relationship between them. From the answer figures marked (A), (B), (C) and (D), pick the figure which most appropriately completes the series.

Let's track the alternation pattern of the elements across figures I, II, III, and IV:
1. Inside the square box (Diagonal line):
* In figure I: The diagonal goes from bottom-left to top-right ($╱$).
* In figure II: The diagonal goes from top-left to bottom-right ($╲$).
* In figure III: The diagonal goes from bottom-left to top-right ($╱$).
* In figure IV: The diagonal goes from top-left to bottom-right ($╲$).
* Following this alternating pattern, the next figure (V) must have a diagonal going from bottom-left to top-right ($╱$).

2. The external rectangular bar:
* In figure I: Placed vertically to the right of the bottom baseline.
* In figure II: Placed horizontally on top of the main horizontal line.
* In figure III: Placed vertically to the right of the bottom baseline.
* In figure IV: Placed horizontally on top of the main horizontal line.
* Following this alternating pattern, the next figure (V) must have the bar placed vertically to the right of the bottom baseline.

Combining both observations for the next figure in the series: It should match the layout of figures I and III (diagonal $╱$ and vertical right bar). Looking at the options, figure (D) perfectly satisfies this layout.