In circle O, which segment is a chord?
A - OH-->
B - SD-->
C - OR-->
D - RC-->
A chord of a circle is a straight line segment whose endpoints both lie on the circle.
More generally, a chord is a line segment joining two points on any curve, for instance an ellipse.
A chord that passes through a circle's center point is the circle's diameter.
Every diameter is a chord, but not every chord is a diameter.
The first choice, OH is not a chord, it is the radius of the circle.
SD is also not a chord, it is a tangent line to the circle.
OR is too, not a chord, it is also a radius.
RC is a chord, since a diameter is a chord.