Group the given figures into three classes using each figure only once.

Concept: In figure-classification (grouping) questions, group figures by finding the shared INTERNAL CONSTRUCTION RULE linking a sub-set of figures - how an inner element relates to the outer boundary (a nested similar shape, an inserted symbol, or dividing lines) - not by the outer shape's identity (circle, square, triangle) or by surface-level similarity.

Application: Examining the seven figures against this rule:

• Figures 1 and 3 each contain a V-shaped (chevron) insert placed inside the outer boundary - a pentagon in figure 1, a square in figure 3 - so despite different outer shapes, both follow the SAME insert rule.

• Figures 2, 4, and 5 each contain a smaller, similar shape nested inside and touching the outer shape's boundary: a smaller circle inside a circle (2), a smaller square inside a square (4), a smaller triangle inside a triangle (5).

• Figures 6 and 7 each have their outer shape divided into four equal parts by two mutually perpendicular straight lines: a circle divided by a cross (6) and a square divided by an X (7).

Cross-check: Each class uses exactly one consistent internal-construction rule, and all seven figures are used exactly once across the three classes - confirming the partition 1,3 | 2,4,5 | 6,7.

This matches the grouping 1,3 ; 2,4,5 ; 6,7.