Hint: The amount of surface enclosed by a closed two-dimensional figure is measured by the number of unit squares it takes to cover a two dimensional shape.
Complete step-by-step answer:
A two-dimensional figure, also called a plane or planar figure, is a set of line segments or sides and curve segments or arcs, all lying in a single plane. The sides and arcs are called the edges of the figure. The edges are one-dimensional, but they lie in the plane, which is two-dimensional.
The endpoints of the edges are called the vertices or corners. If all the edges are segments, every vertex is the endpoint of two sides, and no two sides cross each other, the figure is called a polygon. Polygons are classified according to the number of sides they have, which equals the number of vertices. Here are some names of polygons.
Polygons often divide the plane into two pieces, an inside and an outside. The inside part is called the region enclosed by the figure. The name of the figure is also commonly used for this region, and the area of the region is commonly called the area of the figure.
The amount of surface enclosed by a closed plane figure is called its area.
Hence, the answer is area.
So, option (A) is the correct answer.
Note: In mathematics the area of a plane figure refers to the number of square units the figure covers. The area is the inside shape or space measured in square units. In rectangles and in squares, a simple calculation of length and width will give the number of square units.