ANS:C - an inclined plane surface

A true flat surface will not be represented by widely space contours but it will wholly be contained between two contours very far from each other. In the case of inclined plane surface, the lines of equal elevation are straight (as a mentioned plane) and thus are parallel. Thus C is the right answer. Widely spread: flat ground.
Close together: steep ground.
Uniformly spaced: uniform slope.
Straight, parallel and equally spaced: plane surface. Space between contour represent elevation difference.

In a flat surface, as elevation difference is very less thus widely space contour is used. As we know a particular contour line represents one particular elevation.