We will consider all of the options in detail first. Distance is the separation between two points on a plane, and is calculated by squaring the difference in the y and x values, adding them and then taking their square root. A line is a one-dimensional set of points that extends infinitely far in only one dimension. A plane is a flat, two-dimensional surface that extends infinitely far in two dimension. A point is usually an element within the plane being considered. This exists in 0-dimensions. Therefore, the answer is C. plane.