Select the alternative which represents three out of the five alternative…

Concept

In a figure-formation (embedded-figures) reasoning question, the five alternative figures are pieces cut from one target figure. To identify the three that reconstruct it, every edge of a candidate piece must match, in length and angle, the edge of the piece next to it in the target shape, and the three assembled outlines together must trace the target's complete boundary with no gaps and no overlaps.

Application

The target square in this item is divided by internal lines into three regions: a wide lower region with a horizontal top edge and slanted sides widening toward the bottom, a narrower upper-right region whose slanted edge runs from a short vertical divider down to the square's right edge, and an upper-left region whose defining feature is one long diagonal edge running almost the full height of the square (alongside a short top edge and a short vertical edge). Matching outlines: the wide lower region's shape matches figure (2), the trapezoid. The upper-right region's shape matches figure (3), a small quadrilateral of comparable size and angle. The upper-left region's long diagonal matches figure (4), whose single long diagonal edge is its defining feature. Fitted together, figures (2), (3) and (4) reproduce the square's boundary exactly, so the set "234" is the answer.

Cross-check

Figure (1) has a small re-entrant (concave) notch that none of the three regions contain, so it cannot replace any of them without leaving a gap or overlap. Figure (5) has a stepped, zig-zag edge; none of the three regions has a matching staircase boundary, so putting figure (5) in place of either the base region's slanted edge or the upper-left region's long diagonal leaves that boundary jagged instead of straight. This rules out "124", "345" and "235".