The best approximation for the circumference of the circle is; 1570 km
We are given;
Diameter of circle; d = 500 km
Radius is; r = d/2
r = 500/2
r = 250 km
Formula for circumference of a circle is;
C = 2πr
Where π = 3.14
Thus;
C = 2 × 3.14 × 250
C = 1570 km
Read more about circumference of a circle at; https://brainly.com/question/12823137