What is true about the angle in a circle formed by two radii?

The angle formed by two radii in a circle is indeed called a central angle. This type of angle is created when two radii extend from the center of the circle to any point on the circumference, thus "central" signifies its vertex is located at the center of the circle.

The significance of a central angle lies in its relationship to the arc that it intercepts on the circle, as the measure of the central angle is equal to the measure of the arc formed between the two points on the circumference. In contrast, an inscribed angle, which is formed by two chords originating from a point on the circumference, would have different properties and measurements in relation to its intercepted arc.

While a central angle can indeed measure less than or equal to 180 degrees, this is not a defining characteristic, as there are many instances where central angles are right angles or even acute. An angle that subtends an arc greater than 180 degrees at the center will result in the central angle having to be less than 180 degrees for any practical geometric considerations. Nonetheless, this does not change the fact that these characteristics do not define the angle itself as "central." Thus, the correct identifying feature is that it is genuinely classified as a central angle.