Group the following figures into three classes on the basis of identical proportions

1, 2, 3; 4,5; 6, 7 1, 3, 4; 2, 8; 5, 7 1, 3, 6; 4, 8, 5; 7 1, 3, 4; 5,6; 7, 8

1, 3, 4; 2, 8; 5, 7

We can see: Figures: 1, 3, 4 ⇒ Triangular figures Figures: 2, 8 ⇒ Quadrilateral figures Figures: 5, 7 ⇒ Circular figures Therefore, the correct answer is: 1, 3, 4; 2, 8; 5, 7