Question

which circle has the radius labeled in red?

Explanation:

Step1: Recall the definition of a radius

A radius of a circle is a line segment from the center of the circle to any point on its circumference.

Step2: Analyze each circle

• First circle: The red line passes through the center and has endpoints on the circle, so it's a diameter (twice the radius), not a radius.
• Second circle: The red line has one endpoint at the center and the other on the circle, so this fits the definition of a radius.
• Third circle: The red line is the circumference (the perimeter of the circle), not a radius.

Answer:

The second circle (the middle one) has the radius labeled in red.