Final answer:
The subject of this question is mathematics. 4-sided shapes can have different shapes and angles, and they do not necessarily have 2 pairs of equal sides.
Step-by-step explanation:
The subject of this question is mathematics. The question is asking about the characteristics of 4-sided shapes. The options given are: a) all have a round shape, b) cannot have a long shape, c) do not maintain any shape, d) vary in shape.
The correct answer is d) vary in shape. 4-sided shapes can have different shapes and angles. Some examples of 4-sided shapes include rectangles, squares, trapezoids, and parallelograms.
These shapes can have different side lengths and angles, and they do not necessarily have 2 pairs of equal sides.