1. **Problem Statement:** We need to understand the difference between a line, a ray, and a line segment, and identify which one has a fixed length. 2. **Definitions:** - A **line** extends infinitely in both directions and has no fixed length. - A **ray** starts at one point and extends infinitely in one direction, so it also has no fixed length. - A **line segment** has two endpoints and includes all points between them, so it has a fixed length. 3. **Explanation:** - Since a line and a ray extend infinitely, their lengths cannot be measured or fixed. - A line segment is bounded by two endpoints, so the distance between these points is the length of the segment. 4. **Conclusion:** - The **line segment** is the one with a fixed length. This is a fundamental concept in geometry about different types of straight figures.