How can a graph you visualize reflections

To visualize a reflection across the x-axis, imagine the graph that would result from folding the base graph along the x-axis. You can visualize a reflection across the y-axis by imagining the graph that would result from folding the base graph along the y-axis. 

Cultural convergence is the theory that two cultures will be more and more like each other a very notable example of this is around the u.s.-mexico border, where 

The answer is    d.  central highlands