Which of the following is defined using the undefined terms $\mathrm{point}$ and $\mathrm{line}$?

• A. $\mathrm{circle}$
• B. $\mathrm{angle}$
• C. $\mathrm{parallel} \mathrm{lines}$
• D. $\mathrm{ray}$

Answer: (B)

Verified step by step guidance

1. Understand that in geometry, some terms are considered 'undefined' because they are the basic building blocks from which other concepts are defined. The terms 'point' and 'line' are such undefined terms.
2. Recognize that an 'angle' is defined using two rays (which themselves are defined using points and lines) that share a common endpoint (a point). So, the concept of an angle depends on points and lines indirectly through rays.
3. Consider the other options: a 'circle' is defined using a point (center) and a distance (radius), 'parallel lines' are defined as lines that never intersect, and a 'ray' is a part of a line starting at a point and extending infinitely in one direction.
4. Since 'angle' involves two rays meeting at a point, and rays are defined using points and lines, the angle is the concept most directly defined using the undefined terms 'point' and 'line'.
5. Therefore, to identify which concept is defined using the undefined terms 'point' and 'line', analyze the definitions of each option and see which one fundamentally relies on these undefined terms.