The statement "That does not extend in both directions." will make the definition, precise.
Kevin's line segment definition is correct.
However, the end points in a line segment implies that the line segment does not extend past its two end points.
So, to make it precise;
Kevin needs to include that the line segment does not extend in both directions, in the definition.
Hence, option (c) is correct.
Read more about line segments at:
brainly.com/question/19203823