### Classification

1. Explanation:

In all other figures, the two line segments are parallel to each other.

2. Explanation:

The lines outside the shaded circle are not equally distributed along the circumference in fig. (2).

3. Explanation:

In all other figures, the arrow and the V sign lie towards the black end of the main figure.

4. Explanation:

The pins, equal in number to the number of sides in the main figure are attached to the midpoint of a side of the main figure in case of figures (2), (3), (4) and (5). In fig. (1), these pins are attached to a vertex of the main figure.

5. Explanation:

In all other figures, there are two small line segments towards the pin and three small line segments towards the arrow.
6. Explanation:

In all other figures, the lower-right quarter portion is shaded.
7. Explanation:

All other figures are divided into equal parts.
8. Explanation:

All other figures can be rotated into each other.
9. Explanation:

Only in fig. (3), the line segment is not a diameter of the circle.
10. Explanation:

No answer description available for this question
11. Explanation:

Each one of the figures except fig. (2), consists of five arrowheads.
12. Explanation:

Figure (4) is formed by four line segments while each one of the other figures is formed by three line segments.
13. Explanation:

In each one of the figures except fig. (3), the two crosses (x) appear in the diagonally opposite corners.
14. Explanation:

In each one of the figures except fig. (5), two arrows point towards left and one arrow points towards right.
15. Explanation:

Only in fig. (5), the arrowhead along the circumference of the circle indicates motion in an ACW direction.
16. Explanation:

All other figures can be rotated into each other.
17. Explanation:

In all other figures, as we move from the innermost to the outermost element, the numbers of sides of the elements either increase or decrease in a sequence.
18. Explanation:

Figure (1) and fig. (3) can be rotated into each other and fig. (4) and fig. (5) can be rotated into each other.
19. 20. 