Which of the following has a definite length?
`bar(AB)`

Answer

To determine which of the given options has a definite length, we need to analyze the three geometrical concepts: a line, a line segment, and a ray.

### Step-by-Step Solution:

1. **Identify the Concepts**:
- **Line**: A line extends infinitely in both directions and has no endpoints.
- **Line Segment**: A line segment has two endpoints and a fixed length.
- **Ray**: A ray starts at a point and extends infinitely in one direction.

2. **Analyze Each Concept**:
- **Line**: Since it has arrows on both ends, it does not have a definite length. It continues forever in both directions.
- **Line Segment (AB)**: This is the segment between points A and B. It has fixed endpoints A and B, meaning it has a specific length that can be measured.
- **Ray**: A ray has one endpoint and extends infinitely in one direction. Therefore, it does not have a definite length.

3. **Conclusion**:
- Among the three concepts, only the **line segment AB** has a definite length because it is bounded by points A and B.

### Final Answer:
The line segment \( \bar{AB} \) has a definite length.

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