1. The problem asks to identify the highlighted part of circle O. 2. Important definitions: - A **central angle** is an angle whose vertex is the center of the circle and whose sides are radii. - An **inscribed angle** has its vertex on the circle and its sides are chords. - A **diameter** is a chord passing through the center. - A **chord** is a segment with both endpoints on the circle. 3. From the description, segment CZ is highlighted. Points C and Z lie on the circumference, and segment CZ connects them. 4. Since CZ connects two points on the circle but does not pass through the center O, it is a chord. 5. The highlighted part is therefore a **chord**. Final answer: chord