a line
the flat surfaces of a solid figure are the
One of the figure which has no flat surface is Sphere.
a polygon
The term area is generally reserved for a two-dimensional polygon, but surface area is the term of the area of the different surfaces on a three-dimensional figure---the faces on the object. So no, they are not the same.
Yes, because a polygon is a plane (flat) figure. By definition, if it is not flat, it cannot be a polygon.
face
It is a face of the 3-d figure.
A face
The answer is surface area.
The flat surface of a solid figure is called a face. For example, a rectangular prism has 6 flat surfaces and therefore 6 faces.
A face is the flat surface on a solid figure. For example, a triangular prism has five flat surfaces and therefore five faces.
A surface is a 2-dimensional manifold. Most surfaces are curved, in which for a small "differential" section of a surface, a plane figure is uniquely determined.