Answer:
 the most elliptical orbit is that of COMETA
Explanation:
The eccentricity of a curve in defined as the ratio between lacia to the focus, called c and the value of the axis greater than
          ε = c / a
 if we use Pythagoras' theorem
          c = 
    substituting
            ε =  
if   ε = 0 we have a circumference
In the diagram presented the orbit of the comet is an ellipse a> b
           ε= 
if we expand in series
              ε = 1 - x/2  
              ε=   
if we neglect the non-linear terms
             ε = 1
Earth's orbit is a small ellipse
              b / a = 149 10⁶ / 151 10⁶
              b / a = 0.98675
              ε =  
                ε = 0.16
a very small ellipse
Planet X, despite not having data, it seems that the sun is in the scepter of the orbit, so b = a
therefore  both the semi-axes of the curve
         e = a / b
Consequently, the most elliptical orbit is that of COMETA.