A line segment has dots on both ends of the line. A line has nothing at either end of it. A ray has an arrow at one end of the line. Line BC is a line segment.
This is because we have two fixed endpoints, B and C, where the line does not go on forever beyond those endpoints. This means BC is some fixed length. The terms "line segment" and "segment" are the same thing.
A ray on the other hand would have the line go on forever in one direction, while it only has one fixed endpoint. As the name suggests, think of the ray of sunlight as an example. So we can rule out "ray". We can also rule out "line" because it doesn't extend forever in both directions.
