Question

what is $overline{op}$? center chord diameter

Explanation:

A chord is a line - segment that connects two points on the circumference of a circle. Since $\overline{OP}$ connects two points $O$ and $P$ on the circle's circumference and does not pass through the center $N$, it is a chord. A diameter passes through the center of the circle and a center is a point, not a line - segment.

Answer:

B. chord