What is the perimeter of a circle called?
(a) Circumference
(b) Area
(c) Diameter
(d) None of these

Hint: We will first understand the concept of terms perimeter, circumference, area and diameter. And then form a check which of the given options is the perimeter of the circle.

Complete Step-by-Step solution:
Perimeter is a term used for closed figures. In any closed figure, the length of the line or path that forms the boundary of two of the two-dimensional figures is called its perimeter.
Now, circumference is a term related to only circles. It is the length of the boundary of the circle.
Whereas, area is a term related to all two-dimensional figures. It is the surface of the figure or we can say that it is the space that the figure occupies.
And, diameter is a term related to a circle. This is a straight line joining two points on the circumference of the circle and passes through the centre of the circle.
So, by definition, the perimeter of the circle will be the length of the line which forms the boundary of the circle. Which is nothing but the circumference of the circle.
Hence, the correct answer is option (a).

Note: Students sometimes confuse perimeter to the term related to only polygons, which is wrong. Perimeter is a term used for all types of closed figures and hence applies to circles as well.