Is the dotted line a line of symmetry?
The correct answer is "Yes".
A line of symmetry is a line that cuts a shape exactly into matching halves. This means that, if we fold the shape along the line of symmetry, both halves would match each other.
Given the shape below.
Visualize folding this shape along the dotted line.
We observe that, on folding, both parts match exactly each other.
So, the dotted line is a line of symmetry of the shape.