To solve the problem, we need to identify the pattern or sequence in the given diagram and find the appropriate figure to fill the blank space.

Looking at the sequence provided, let's examine each figure step by step:

1. The pattern consists of similar triangular shapes with varying sections filled in black.
2. The first figure has a small black triangle in one corner.
3. The second figure shows the black area shifted and expanded slightly.
4. The third figure continues this pattern with incremental changes, including an added white dot.

The sequence suggests that each subsequent figure adds complexity by shifting and expanding the black area while introducing a white dot strategically.

The task is to determine how the pattern evolves in the next step. We observe:

1. The black area should continue to shift and expand.
2. The position of the white dot might also need to change slightly to maintain consistency.

Now, let's compare this logic with the options provided:

Comparing with the correct answer:

This option aligns with the observed pattern of continued black area expansion and strategic placement of the white dot. It logically follows the sequence, completing the pattern.

Therefore, the correct figure to fill in the blank space is:

This choice completes the progression appropriately, adhering to the pattern observed.