To determine a line of reflection that would flip the hexagon onto itself, we need to find a line that is equidistant from corresponding points (or vertices) of the hexagon on either side.
Since the hexagon is in quadrants 3 and 4, and we are looking for a line of symmetry, we can consider the x-axis, which is represented by the equation \(y = 0\). This line would reflect points in quadrants 3 and 4 onto themselves.
Therefore, the correct answer is:
y = 0