What is a segment, ray, line, or plane that intersects a segment at its midpoint

Point- an exact loction in space with indefinite shape and size.
line- an object with no thickness that extends infinitely in 2 directions.
line segment- a portion of a line consisting of 2 end points and all point in between.
ray- a portion of a line consisting of 1 end point and all point in between.
opposite ray- 2 ray sharing the same end point and continuing infinitely in 2 direction.
plane- a flat surface that extends infinitely in all direction.
collinear- point that lie on the same line.
non collinear- point that do not lie on the same plane.

Ithink the answer is a