What kinds of polygons are symmetrical? a. circles b. scalene triangles c. all regular polygons d. none of these

A shape is symmetrical if it can be divided into equal halves.

A circle unfortunately is a not a polygon. A circle is symmetrical. It has infinite lines of symmetry.
(A circle in theoretical sense can be said to be a polygon with infinite number of lines...)

Scalene triangles are not symmetrical because, each of the three sides are not equal.

The answer is C. all regular polygons.

All regular polygons are symmetrical.

Example a square has 4 equal sides has 4 lines of symmetry.

A regular pentagon which has 5 equal sides has 5 lines of symmetry.

So the correct answer is C.   

The answer to your question is the last one