This question tests understanding of geometric analogies.

Geometric Analogy: Line, Square, Arc, Circle

The first pair establishes a relationship: A line is the basic component used to construct a square. A square is a closed, two-dimensional shape made of four straight line segments.

We need to find a similar relationship for the second pair, starting with an arc. An arc is defined as a portion of the circumference of a circle.

Following the pattern, the component (arc) relates to the whole shape it is part of. Therefore, an arc is a component of a circle.

The complete analogy is: Line is to Square as Arc is to Circle.

Conclusion: The shape associated with an arc is a circle.