Let's analyze the question step-by-step to find the correct answer.
1. Understanding the Question:
- We are dealing with a line that does not touch an object.
- The choices provided for the type of line are: extension, hidden, center, and dimension.
2. Evaluating Each Option:
- Extension Line: These are lines used primarily in technical drawings to extend the edges of objects to measure distances. An extension line marks the extent of a dimension but does not describe the position of an object.
- Hidden Line: These are typically dashed lines that represent edges or boundaries of an object that are not directly visible. They are used to indicate edges that are obscured by another part of the object.
- Center Line: These lines represent axes of symmetry in drawings. They often mark the center of circles, cylindrical features, or symmetrical parts.
- Dimension Line: These lines are used in technical drawings to show the size or location of features in a clear and precise manner.
3. Common Characteristics:
- A hidden line is unique in its purpose to indicate parts of the object that are obscured from view. All other lines (extension, center, and dimension) usually are drawn in relation to the visible or specified part of the object.
4. Conclusion:
- Based on our analysis, the type of line that does not touch the object directly and represents parts that are not visible is most accurately described as a "hidden" line.
Thus, the correct answer to the question is:
b. hidden.
