Question

Which is the most precise definition of a​ circle?

A.
A line that is curved so its ends meet
B.
Shape a compass draws
C.
The set of all points in space that are equidistant from a fixed point
D.
The set of all points in a plane that are equidistant from a fixed point

Answer 1

The best answer is D.

A is incorrect because that means that all squigly lines that have ends that meet are circles, which is false.
B is incorrect because this is not very precise as a definition. Also, compasses are not completely perfect, so the points are slightly off from being completely equidistant from the point.
C is incorrect because that's describing a sphere (notice how it says space instead of plane).

Answer 2

D. The set of all points in a plane that are equidistant from a fixed point.