Concept:A line segment has two fixed endpoints, so its length is fixed and measurable. In contrast, a ray, line, and plane extend infinitely and thus have no definite length.
Explanation:A line segment is bounded by two distinct endpoints. It therefore has a specific, measurable length.
A ray starts at one endpoint but extends infinitely in one direction. So its length cannot be determined.
A line extends infinitely in both directions. It has no definite length.
A plane is a flat, two-dimensional surface that extends infinitely. It has area but no one-dimensional length.
Only the line segment meets the condition of having a definite length.
Answer:Option A (a line segment)