Answer:
In geometry, undefined terms refer to point, line and plane definitions. Basically, they are the fundamentals to build the rest in Geometry, they are some primitive, their concepts are so intuitive, that there's no actual defintion of them.
So, among the options, we just need to look for a point, a line or a plane. Notice that the last choice is a line, because it has no ending point (the arrows indicate that it's infinite).
Therefore, the last choice, the line, is an undefined term.
Additionally, you may think that the first choice is also an undefined term, but the reason is not is becuase it's a ray, which is defined as a semi-line, which originate in a certain and defined point to the infinte.
