Correct Answer
The line through the circle is a line of symmetry. The diagonal line through the rectangle is not a line of symmetry. The line through the 12-sided shape is a line of symmetry.
Explanation
A line of symmetry divides a shape into two equal parts, where one part is the mirror image of the other. When you fold the shape along the line of symmetry, both sides should match perfectly.
In a circle, any line that passes through the center divides the circle into two equal halves. If you fold the circle along that line, both sides will overlap perfectly. This happens because in a circle, all points on the edge of the circle are the same distance from the center. Since both halves of the circle are equal and mirror images of each other, the line through the center is a line of symmetry.
A line from one corner (vertex) of a rectangle to the opposite corner is called a diagonal. A non-square rectangle has two pairs of sides: two longer sides and two shorter sides. When you draw a diagonal from one corner to the opposite corner, it divides the rectangle into two triangles. However, these two triangles are not identical because one triangle will always have a shorter side and a longer side, and the other triangle will have those sides reversed. Therefore, if you tried to fold the rectangle along the diagonal, the two halves would not match exactly. The two triangles created by the diagonal are not mirror images of each other. This is why a diagonal line in a non-square rectangle is not a line of symmetry.
For the third shape, the horizontal line through the middle of this 12-sided figure divides the shape into two equal parts. If you fold the shape along the line, the edges of the shape would line up perfectly. The line is therefore a line of symmetry.
