Sure, let's analyze the concepts listed and determine which one is defined using the undefined terms "point" and "line."
1. Angle: An angle is formed by two rays with a common endpoint called the vertex. It involves more defined terms such as rays and vertices, which in turn are defined using more basic terms, not directly points and lines.
2. Circle: A circle is defined as the set of all points in a plane that are at a given distance from a given point called the center. The definition of a circle uses more terms than just point and line.
3. Parallel lines: Parallel lines are defined as lines in a plane which do not meet; that is, they do not intersect. This concept involves lines directly but the term "parallel" is an additional term defining a specific relationship between those lines.
4. Ray: A ray is defined as part of a line that starts at a particular point (called the endpoint) and extends infinitely in one direction. This definition directly incorporates the undefined terms "point" and "line."
Since a ray is defined using only the point and line, it is the correct answer.
So, the answer is:
Ray
